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@Red13: yes, this is totally possible and one UWB device e.g. U1-compatible UWB Beacon can establish connection with several iPhones at the same time.
This require the UWB device to has capable SoC, e.g. Bluetooth chip with the right stack to simply handle several open Bluetooth connections at the same time and then perform UWB ranging.
However this might not be practical since constant UWB ranging will drain battery for both iPhone and UWB device (e.g. UWB beacon).
What will be a better approach is to allow 5 iPhones to quickly range one by one to UWB Beacon and after the distance/angle vector is established disconnect and continue with the position vector using ARKit. This was demonstrated with on the iO16 during the last WWDC Nearby Interaction sessions here: https://developer.apple.com/videos/play/wwdc2022/10008/
That approach drains less energy from the UWB beacon since you only connect from time to time to correct the vector rather that keep constant UWB connection.
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At the moment Nearby Interaction that is using UWB ranging to compute precise distance/angle can be run when the app is in the foreground only and that is a design decision by Apple (probably due to the privacy implications).
What you might try is to use Core Location and/or iBeacon to detect "enter into the range" event that will work in the background (assuming user gave proper permissions).
Once user enters the range of e.g. smart lock then you can push a message to open the app and switch to UWB ranging with Nearby Interaction API once that app is in the foreground.
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It is also possible to connect and range with multiple non-Apple UWB devices that are compatible with U1 chip.
Apple has published here https://developer.apple.com/nearby-interaction/ in the FAQ section a list of recommended UWB chipset manufacturers that are interoperable with U1 chip.
There are already UWB devices on the market integrated with these new chips, e.g. UWB beacons and tags.
Just google "UWB beacons" and get one of the available Dev Kits; they typically come with SDK and you can see there
examples of ranging with multiple beacons at the same time.
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With iOS15 Apple has enabled "Nearby Interactions API" to range and obtain inch-level distance and orientation (similar to AirTags) between Apple U1-enabled devices and third-party UWB-enabled devices compatible with FiRa and U1.
On this website https://developer.apple.com/nearby-interaction/ Apple has published in the FAQ section a list of UWB chip manufacturers that are interoperable with U1 chip.
On the market there are already UWB devices (e.g. beacons, tags) integrated with these recommended UWB chipsets.
Try to google "UWB beacons" and get one of these Dev Kits. They typically comes with SDK full of code samples and demo apps.
It will take minutes to integrate it with your mobile app that can finally be spatially aware.
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As of May 2022 Apple AirTags cannot be used by developers outside their original consumer use-case alongside with FindMy app.
However there are other beacons and tags available on the market that has both UWB compatible with U1 as well as Bluetooth.
In iOS15 Apple has enabled U1-devices, e.g. iPhones to range and obtain inch-level distance and orientation to third-party UWB-devices compatible with U1/FiRa.
Under this link: https://developer.apple.com/nearby-interaction/ Apple has published in the FAQ section list of UWB chip manufacturers that are interoperable with U1.
Just google "UWB beacons" and get one of the available Dev Kits to play around. They are typically shipped with SDK full of code samples and you can easily turn these beacons into iBeacon-like experience where your mobile app can be spatially aware.
Please note as or right now Nearby Interactions API only allows ranging in the background, so your app cannot do that in the background. For this you would still need Core Location API with classical iBeacon packet and user permissions, e.g. "Always on".
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In iOS15 Apple has released "Nearby Interaction API" that allows U1-enabled iOS devices to range and calculate distance/orientation to nearby UWB-enabled tags or beacons similar to AirTags.
On this website: https://developer.apple.com/nearby-interaction/ Apple has published list of chipset manufacturers that have UWB chips compatible with Apple U1.
There are already UWB beacons, tags and anchors on the market that are compatible with U1 and FiRa, so you can simply google and get Dev Kit to play around and build your own "AirTag"-like finding experience.
There is also FindMy network program, but that is a separate story.
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With iOS15 Apple has released "Nearby Interactions" API that allows U1-enabled Apple devices to range and obtain inch-level precise distance with other, non-Apple, UWB-enabled devices.
Under this link: https://developer.apple.com/nearby-interaction/ Apple has published a list of UWB chip providers that are interoperable with U1 chip.
Try to google for "UWB Beacons" and you can find many Developer Kits you can get to play around. Just make sure these are compatible with U1 or FiRa, as Apple devices can only talk to devices that are interoperable.
As of May 2022 it is not possible to range with AirTags, however it is possible to range with UWB Beacons manufactured by third-party companies and compatible with Apple U1 chip.
Apple has published on this website: https://developer.apple.com/nearby-interaction/ a list of UWB chip manufacturers,
so you can get simply get devices with these UWB chipsets integrated.
There are many UWB beacons and tags available on the market; just search for the one that are U1 or FiRa compatible.
Simply google "UWB beacons" or "UWB Dev Kit"; they typically come with SDK full of code examples, so it's easy to integrate with.
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With iOS15 Apple has released Nearby Interaction API that allows iOS devices with U1 chip to connect and range with other non-Apple UWB-enabled devices that are interoperable with U1 chip.
Under this link: https://developer.apple.com/nearby-interaction/ you can see in the FAQ section recommended UWB chip manufacturers.
There are many companies offering Dev Kits where these chips were integrated, so you can build iOS app that can do inch-level precise ranging and obtain angle orientation to these 3rd party devices, e.g. beacons.
Just google "UWB beacons" or "UWB Dev Kit" to get some; they typically come with SDK where sample code is provided,
so it shouldn't take long to build spatially aware mobile apps.
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If you want to build your own spatially-aware iOS app that can range and estimate distance/angle to other, non-Apple UWB devices, e.g. beacons you just need to make sure these other devices have the latest UWB chip that is "interoperable" with Apple U1.
Apple has published here: https://developer.apple.com/nearby-interaction/ in the FAQ section the list of chip manufacturers that have compatible radios with U1.
There are many companies offering Dev Kits that have these new, compatible chips already integrated.
Google "UWB Dev Kit" or "UWB Beacons" and get some of these devices. They typically come with SDK full of examples, so it should be pretty simple to integrate with your app.
