As of the release of Radius 3.0, there are new callbacks (event notifications) that are triggered when:
Tone Presence Callback - the very beginning of an incoming tone is first detected. This can be useful for if a long transmission is incoming to let the user know that an event is occurring/to hold steady/etc.
Tone Failure Callback - to indicate when a tone has failed to be demodulated after it has initially been detected. This can be useful for providing UX/UI feedback to the user to perform corrective action to improve detections - hold their phone steady, move closer, etc.
These new features are available to test in the Radius Sample and Radius Experience Applications. Email our Customer Success team to request access (techsupport@lisnr.com)