Telemetry is the "big thing" in 2.4GHz radio systems right now -- but what's it all about.
This video explains some of the basics of telemetry and demonstrates how the Hitec Spectra module/receiver telemetry works to alert you to such things as low-receiver voltage.
I'm also planning to design and build some telemetry sensors and display for the FrSky 2.4GHz system so if you want to have some input into the design process, leave a comment on this video describing what you'd like such a system to offer.