I recommend the Schwinn computer that I got from walmart. (it has the normal stuff of trip, odo, max speed, ave speed, time and temperature) and I have used this on my bike in the rain with no problems and it cost about 10 dollars...

gives picture (though the listed price is higher than what I paid)

http://www.afterschool.com/p/pti-sch...la&cagpspn=pla