The cost is about 40 Euro. The producer is GPT, an Italian producer. I attach link for more informations. This one is the simplest kind of REV produced by GPT. In any case, for my expectation it's very good. It doesn't need to modify the bike. Have an internal battery that is in function from more then two years. The sensor is a cable that work per induction and need only to be near the spark plug cable (see the cable fixed with red strip to spark plug cable, in the attached pictures).
It's settable for avery kind of engine. Of course it depends on what you are looking for. But, I repeat, in my opinion is very usefull (set up and so on). I would to explain better, but this one is the limit of my English. In any case, if you need further informations, don't hesitate to ask me. I will try to answer. Sorry and best regards. have you a nice day. Gianni.

http://www.gptengineering.it/gpt_eng...MICRO_RPM.html

__________________
Mess with the best, die like the rest.