I do not, however, my radio has an LCD that displays remaining voltage and it also has an alarm that sounds when it reaches below 9 volts... since I use rechargable NiH they always run down before my hump pack because I bought a quality pack and charger therfore I never worry much about not having a fail safe but on the other hand.... $20 is cheap insurance to save a $300 rc car

I have heard alot of good things bout the venom fail safe, but dont get the one with the temp sensor!