integy has some unit that sits inline with your charge cable.

https://www.ssl-stormerhobbies.com/pics/int1484.jpg

Integy`s Thermo sensor simply plugs in-line with your charger and battery pack and turns it into a thermal cut-off charger. Included sensor probe just attaches to the battery and when the pre-set temperature is reached, the unit shuts off the charge current. Simple and effective.
Features:
12 volt power input with aligator clips
Charger input and battery output with Tamiya style connectors, just connect it inline with your charger
Sensor probe tip and strap for easy connections
Adjustable temperature cut-off in degrees Celcius
Handles up to 7 amp charge rates

Hah! ANyone use this? :P (yea I was bored, thumbing tower/stormer/horizon for xmas ideas for myself).

hahaha.