Nothing happens when iPhone is locked. The message is received which you can see after pushing the home button or on/off switch.
Isn't it the main point to get a message (push) when you reach a beacon? Is there some way to make that happen?
iBeacons does not wake up iPhone
How do you test it? If you are always in the region of iBeacon, it won't trigger your code again once it triggers. You need to exit from iBeacon's region and enter again. To simulate it easily, you can remove the battery from iBeacon and wait 30 seconds. Then, plug the battery in and it should trigger.