I've got the Venom Smart Temp if thats what you are referring to. Yes you will need two as they have one heat measuring loop, but they connect to the throttle servo and to your receiver, so you prob don't have enough free connectors.

I'm very happy with mine, very easy to set up, but I'd recommend getting a temp gun too and using it to put the Venom's loop on the right ring of your engine. It says in the manual that you should put it around the lowest ring, but this can measure temperatures higher than the glow plug is actually at. They are very accurate, you just need to make sure its fitted properly to do so.

Here is a picture of mine installed, like a normal failsafe you put the throttle into the Venom, and the venom into the reciever. The heat loop goes around the engine head, you can see mine going around the back and through my strut to the engine:



I don't have the speed meter though