I recently bought a Fitbit Zip pedometer.

Accuracy: Unlike mechanical pedometers, this pedometer has accelerometers and appears to be extremely accurate without calibration. I haven't tested it in the mountains yet. It doesn't miss as many steps as my old pedometer which was pretty good.

Location: The pedometer can be worn most anywhere without affecting accuracy.

Record keeping: The pedometer syncs with the computer or with phones that have bluetooth 4.0 capability. It stores up to seven days of data if there isn't a chance to sync.

Calorie counting: Miles count differently based on the speed and duration. It always updates how many calories have been burned so far in the day and can display that on the pedometer.

Website: The website keeps the data and makes fancy charts for everything.

Battery: It is powered by a watch battery that lasts 4 to 6 months. There is an indicator on the website showing the amount of charge left.

Advantages for hiking:
Distance hiked: This can be useful for a person who doesn't carry a GPS: I'll have to test it to see how accurate it is.
Altitude change: It measures the distance climbed and descended.
Wasted steps: On the website, the graph displays the steps at different times of day. If it's important to a backpacker, they will see how many steps they walk after "stopping" for the day.
Weight loss: Calorie counters can input foods eaten and discover if they are going to gain or lose weight.