I am aware of some of the telemetry options. I have a Taranis altitude sensor in my 1/4 scale Cub.The first time I flew with it I left the audio reporting turned off until I was at 400ft by my judgement, then turned it on and it reported 590ft. It made me aware of how hard it is to judge altitude.
The DRCE field is directly under the approach to runway 17 and 2.4 miles from Centennial Airport Englewood, Co. Normally the airplanes approaching are at 1000 to 1500 ft above the field but on Monday one came by approx. 500 to 600 ft and a large model was flying at the same time. The Gulf Stream pilot reported a near miss to the tower and we had police on the field within 15 minutes.
Approx. 75% of the models at DRCE are small electric but they also exceed the 400ft restriction at times. It is unlikely that this type of model is going to utilize telemetry and I was looking for a way the club could monitor model altitude. I quit flying my jets at this field 6 years ago because of the restrictions.