Okay - another update!
I've updated the software and now rather stupidly put it on the bike. Stupidly because it's probably going to be raining when I ride in tomorrow, and it's not water resistant!
Anyway, here are a few pictures:
The sensor is attached to the rear mudguard - one of the few places where I could be sure of it not getting obscured:
The cable winds back underneath the rack and winds around the seatpost:
None of my project boxes would fit it, so until I get something better, the circuit board and battery are currently stuffed in with my Smart headlight lead acid battery:
Finally, here's the display, held in place with an elastic band:
Basically it displays the closest distance it's detected in the last few seconds.
I'll report on it's performance tomorrow!