i remember reading on here about something people were using but cant remember what it was ?

anyways im looking for something i can buy and put in my car that will be reasonably accurate and give me data of 30 - 130 time, 0 - 60 time etc.
im sure ive read about something available somewhere anyone any idea what im on about ? lol

this is it but are they any good ?

http://cgi.ebay.co.uk/Gtech-Pro-RR-P...item19b5b934bf