Openmoko™ is a project to deliver mobile phones based on open source software. That sounds like a pretty ambitious plan to me, but all power to them.
Yesterday Joseph Reeves linked to my Walter post, to support a suggested feature for OpenMoko, and it's generated a burst of activity on my blog.
If someone does attempt this, then here is another suggestion.
On my GPS I can tell how far my alter ego is ahead or behind me in distance - but not in time. More importantly I can't compare my current speed with the speed I managed at the same point on the original trace. So until I get home, the only way I can tell if I am going slower up a particular part of the climb, or bottling out of going faster down a steep hill is whether the gap is increasing or decreasing. What's more, let's assume Walter is ahead of me going up a hill. He reaches the top first, and starts to accelerate down. So the gap increases, even if I am now climbing the hill faster than he did.
So in practice, once I've fallen behind it's very difficult to know whether I am catching up or not, except over quite a long stretch. Not that this is very important, but it would be a bit useful.