Get the Garmin 305 with the Heart Rate and Cadence Sensor -- You're done!
I bought a Foretrex 101 last year and like it. You can download route data into it set it to tell you the next waypoint along your roué. Nice thing about this is that it runs on two AAA batteries so it was easy to "recharge" the device when the batteries died.
Then this year I got a Garmin Edge 305. Nice unit. Has the cadence and the heart rate built right into it. Tracks your route. Everything is wireless and the speed/cadence unit is very small compared to others. If you have the City Select software it will even overlay our route on the map once you download the data to the PC. Also, you can set the thing up to display eight fields of data about your ride (like altitude, heart rate, cadence, incline, altitude, elapsed time, etc.)
The only thing that I am wary about in the Garmin Edge 305 is the rechargeable battery. If you go on a multi-day ride you have to find a plug to recharge it in (probably not too much of a hassle -- find a restaurant and plug it in while you're eating). The charge from the walk-brick is good for 12 hours. I haven't reached the "now I am turning off " discharge state point yet, but also haven't been on a ride longer than four hours with it yet either. Also charges when hooked up to your computer through the mini-USB connector.
So, I use both on my bike now. The Foretrex 101 to download a route to and have it set to track the route and keep me abreast of the next waypoint (also keeps me motivated on the ride) and the Garmin Edge for the real-time speed, heart rate, cadence, and route statistics. I have them both hanging off a Minoura Swing Grip attached to the goose neck, under and in front of the handlebars -- no handlebar real-estate used up -- all handlebar real estate for the hands. If I do a "Tour de Ville" then the 305 will keep track of the route I took and then I set the 101 unit to keep track of altitude and how far I am away from the starting point. (I'm in Colorado Springs and live in the foothills, so keeping track of the altitude while going up and down the hills is an interesting statistic -- you can get 2,500 feet of climbing in on a 10 mile ride here.)
Obviously, there is some duplication in what is being tracked and in some cases overkill instrumentation. I'll be the first to admit that. The 305 will get you about 90% of what you need to know. If you play with the buttons while riding, it'll get you to about 99%. The added bonus is that there are no wires and clean install. Displays are nice size, easy to read, customizable, and back-lit.
I guess the biggest downside to the 305 is that is bicycle specific. I tried it on a walk and the thing kept on "autopausing" because I was moving too slow. I think you can set this down to a lower speed or turn the autopause off, but I haven't took the time to do it. You probably wouldn't use it for hiking out in the woods.