I think some clarification about the Garmin Fortrex 101 is in order:

1) It uses two AAA batteries. They last for several hour rides at the worst. Carrying two extra AAA's in an under seat bag takes up minimal space and weight. The unit allows you to replace your dying batteries and not lose your current trip data. Purchasing AAA's at COSTCO is pretty economical. If you use your device on EVERY ride - which we don't - you might want to use rechargeables from an environmental point of view.

2) You can download your trip data from the 101 to your Computer and overlay it on a map. I have done this to where a couple of bike paths actually went in relation to the streets and roads we knew.

3) You can also "mark" (and name, if you want) points in your travels to assist in your retracing your route, or in the "mapping" mentioned in #2, above.

If you want to know how far you have gone, time actually moving, average speed while moving, max speed attained and altitude, plus much more. Screens can also be tailored to what you would like to watch as you ride.

It attaches VERY securely to the bike's handle bar.

https://buy.garmin.com/shop/shop.do?pID=260#