Glow driver. This sounds like what you are talking about.
AGS-1 and AGS-2
If you want total reliability from your glow engine, then you need an AGS on-board glow driver.
The AGS Glowswitch is still the only glow driver that monitors the glow temperature and heats the glow-plug only when necessary so only a small (light weight) support battery is needed and there is no risk of damage to the plug. Unlike other glow drivers, the AGS supports the glow even at high throttle settings so, for example, an aborted approach need present no problems; you just open up the throttle and the engine responds as desired.
The Advanced Glowswitch (AGS) has all the features of the well known original Intelligent on-board Glowswitch (IG), but in addition it:
Ø Automatically adjusts to any support battery voltage from 1.2V to 4.2V.
Ø Works with a receiver voltage of up to 7.2V.
Ø Is suitable for all battery types including LiPo, LiFe, Lead-acid and NiMH.
Ø Needs no Y-lead connection.
Ø Optionally fully automatic or transmitter controlled.
Ø Has remote ultra-bright, daylight viewing, indicator LEDs connected with mini screw terminals.
Ø Has a remote adjustment panel also connected with mini-screw terminals.
Ø Automatically compensates for battery voltage fall-off in use.
Ø Has simple two-terminal plug connections (three terminals for the twin version).
Ø Still has the Start-Up Boost feature.
The LED(s) tell you when the AGS is testing the glow and when it is boosting it. They will also give you information about your glow and receiver batteries – indicating the type of battery it has detected and whether or not the battery is getting low.
The AGS turns off when the Rx is switched off, so you can leave everything permanently connected, ready for starting and the next flight.
Installation is easy. Just connect the support battery and the glow plug to the AGS and plug the AGS into the Rx. Full instructions are provided with each unit and in the Advanced Handbook.