I'm posting this as it may be of interest to some of you.
As part of trying to rebuild my fitness and start some serious walking again, I decided initially to get a pedometer type app so I knew how far I'd walked and at what speed. Then I decided that it would be nice to be able to record the track I'd walked and be able to display that on a map or on Google Earth.
At the moment I'm using Ultra GPS Logger, and am very impressed with it. It's not just for walking - it can be used to record any form of travel, from flights and driving, to swimming (although the mobile might object to that!).
It's configurable in all sorts of ways. For example, you can set it to only log a position every so many seconds, and not use GPS (and battery) all the time.
Margaret's just tested it by walking back from Rafal, and when I displayed her track in Google Earth, it was spot on, as was distance and average walking speed.