Dynamite's Large Scale Safety Kill Switch allows you to shut off the engine from a button you assign on the transmitter. 
Features:
Works on any gasoline engine, with a magneto drive ignition (not compatible with CDI driven ignition)
Remote LED to indicate if the ignition is live
Fiber optically coupled to eliminate interference
LiPo/LiIon/LiFe/NiCd/NiMH compatible
Voltage input range from 3V - 3A to 20V - 16A
Surface mount technology
High quality wiring with universal servo connectors
Only 0.3 oz/8g
Manually shut off engine from assigned button on transmitter
Automatically shuts down power to the ignition on loss of signal or low voltage