Just tried installing it on my commute in London. Didn't work - in fact it thought I was at the stop before the one I got on at (when I did have GPS) even when I was 5 or 6 stations further along on my journey. Then it spent the whole rest of the journey spamming me with notifications about the next departure time at the station I didn't get on at.
Wildly inaccurate even with GPS it seems.
Instant uninstall. Sorry.