Garmin foretrex 101 or 210. I have used one for a couple of years and am a staisfied user. The 101 uses AAA batteries - alkalines, rechargeables, or lithiums, while the 201 uses a proprietary rechargeable. Either unit can interface with a computer (cable is extra, I believe) for downloading or uploading waypoints. The 101 is slightly cheaper (about $100); I also prefer the flexibility in batteries.

The unit is lightweight (about 3 oz), accurate (to within 3M), and easy to use. It only displays tracks, routes, and way points, so it is best used with a paper map, something you should carry anyway.

My 101 shows altitude and I find it to be quite accurate, although it does not does not contain an separate barometer. Thanks to recent street work in my neighborhood, I know the ekevation of my hour to the nearest foot. My 101, when given a minute or two to settle in after activation, will routinely give an elevation within five feet of the true value.

I use it for hiking and it has replaced my bicycling computer, as well. In both applications, it fastens to my wrist with a velcro band. It could also attach to a pack strap or reside within a shirt pocket.

I am just a satisfied user - no commercial affiliation.