If you have never had the chance to experience on-board telemetry, start with an Eagle Tree Systems altimeter. These are so easy to use. Simply plug the altimeter into your receiver and it will log your altitude and hold that altitude in memory until you power off and on or exceed the value of the previous memory. These altimeters are high resolution and require nothing more to be added. The new V4 is fully compatible with the V3, OSD systems and Power Panel LCD products for real-time data.
These altimeters are great fun for soaring and powered glider flight.