Hello HN,
I built www.sftransit.us to make it easier to get live transit arrival/departure times on your cellphone. Right now, it does Muni and BART. You don't have to download anything, and it takes one click to find times for nearby stops.
I don't live in San Francisco right now (but am moving out there in a few months). I'm really keen to know if this is a useful service, and to know if there's anything that would make it more useful to you. I'm aware there are a few existing tools for this (like Routesy, and the official site [of course]), but I don't think any are as hassle free...
http://www.sftransit.us
I don't know if you're planning any of this already but I do have a couple suggestions based on my current frustrations with nextmuni:
1. Favourite buses in addition to favourite stops and prioritise said buses when nearby. I know that 21 and 5 are the two best buses to get me home but when I'm downtown they often aren't even on the nextmuni's nearby list because of the density of buses. I'd love to be able to favourite those buses and have them show up first (or at the very least always show up) if a stop is sufficiently nearby even if I'm at a stop I don't frequent.
2. This one would be a bit more of an involved feature and I'm not sure how feasible it is with whatever dataset and/or APIs you have to work with. Basically, I want to be able to input my destination and have the site serve me buses with stops near both end points (if any exist), giving me time estimates near my current location.
Configuring "nearby" would be handy but far from critical, also.