For general purposes, the lighter may be an OK place to check voltage, but it wouldn't be my first choice as a tech. It's too far from anyplace where the reading would be really accurate and meaningful. The link posted above should be pretty good for what you're doing. For the thermometer, I use one like this:
Amazon.com: Raytek MT6 Non-contact MiniTemp Infrared Thermometer: Automotive. It's accurate, has a long battery life (I've put in maybe 2 batteries in 15 years) and well made. The $20 HF one can't possibly be anywhere near as good as this one, and you'd probably be throwing away your money. The temp range should be good for what you need. Won't read the oak coals in your BBQ, though .....................
The Cap'n