How critical do you need it to be? The one that has to be the most ubiquitous out there is the Radio Shack, the analog-meter model. I use that model because down here in sunny Florida, the PO-lice use it. Works for me, anyway. Of course, I don't have to worry about the needle on the meter freezing up in chilly weather. And for less than $40, it's easily replaced if it gets dropped one too many times. But I must say, I have two of these, and they've been through hell and back, nary a problem.

On the other end of the scale, the Goldline SPL series - though, they are very expensive!