So... I just have a crappy little heart rate monitor and haven't wanted to dish out all the money for a bike computer. But... I did dish it out for a smart phone. For anyone that has a phone with GPS built in, there is a cool application that will track your ride/run (and other distance covering activities) on a map, speed, average speed, per mile speed, distance, altitude schematic over speed and distance, and record it online. Its a free application called Endomondo. Its made by web designers and coders in europe. It lacks some things that a bike computer has. Like cadence, power meter, and the ability to be mounted on the bike. But it is nice to have something just track you rides and speed. Its not perfectly accurate but it gives a good idea. And hey... its free... well... beyond the price of the phone and data plan. So, it may not be the best for real training, since it can't really give that instant feedback. But it is nice for tracking progress, rides, and goals.
Another thing it has the capability of utilizing is a bluetooth heart rate monitor.... which... I have never seen or heard of.
Just thought i'd share the fun of smart phone applications as it applies to cycling!