Planet Bike Protege 9.0

Should be about $35 anywhere you find it. Nice hefty cable, large easy to read display, all the needed features (current speed, max speed, ride time, average speed, total miles, ride miles, total miles per bike, support for 2 different bikes, clock, thermometer)

It's got a sweet buttonless design, basically the whole thing is a button and you slide it in the mount to change modes. Current speed, ride time, and ride miles are always displayed.

EDIT: it doesn't do cadence, but who cares, just keep pedaling and keep your heart rate up. You can figure cadence out easily on your own. One complete turn every second is 60rpm, so to get your target cadence just go from there. 90 = 1.5 turns per second, 120 = 2 turns per second, 180 = 3 turns per second, etc. Spend a minute or two really concentrating on getting your cadence right, then learn how the correct cadence feels. Now just stay there.