We've toyed with taglines at the top and once the iPhone app/Android app were done we wanted to use that space to advertise. We definitely need to work something short back in there.
We have a few different ideas for monetization; the most obvious one is auctioning off that 'hot tweet' area on a nightly basis; that is seen by every web/mobile user. I like it because these are advertisements our users would actually want to see.
Btw, I'm not your target demographic, but I have to say you have a nice useful app. Kudos all around.
- the UI makes sense if I bother to spend more than 30 seconds playing with it, but it's hard to tell what it does at first. Maybe add a tag line or a brief description for the non-mobile users.
- has actual content for major cities that are not in the US. Impressed.
- looks polished overall
- how are you monetizing?