Perhaps you are thinking of an electronic cut off switch. This is a Tx controlled
way to shut off the motor. Some guys use a servo to drive the choke closed and
provide the same function. You should have one or the other. In either case
you will have something plugged into the Rx. For the choke impemented
cut off it will be the servo used to drive the choke linkage. For the electronic
switch it will be the line from the sending unit of the electronic switch. I have
had good experience for some years with Electro Dynamic optical cut off
switches. If you need more info on cut off switches go to the Electro Dynamics
web site and they have diagrams showing how the stuff works.

http://www.electrodynam.com/cgi-loca...exe/?E+scstore

I have no connection with ED.
Good Luck