The system checker that Venom makes is a device thats plugs in-line with your battery pack between the battery, and the RX. It blinks at a constant rate to give a constant visual indication that the battery has adequate voltage to run the servos. If the voltage drops below a certain amount, rather than having a run-away vehicle, the LED starts blinking erratically, which is a visual indication of a low RX battery, so you can charge or change the battery pack out. I think its a great product, it takes all the guess work out of the RX battery packs condition. Since I am using a 1700MAH NIMH RX pack, even with all digital Hitek HS5945MG servos which are power hungry, I rarely run a RX pack low. Ive never seen the LED blink erratic yet.
Heres a picture of the unit...I double stick taped it to the inside of the top case.
