Some time ago I've written
about software support for bike speedometer for n900. It was proof of concept CLI realization in Python. Now firs beta of normal application is available. It was rewritten in C++, which decreased CPU usage by four times. For the beginning speed, trip distance, average speed, average speed in last 5 minutes and clock are supported. So this is already a usable solution. Now the main question is "How many people are interested in this and why n900 can be better, than usual bike computer?"