I'm not sure about SMS, however someone somewhere did mention the idea of a lightweight client to use on smartphones. I am not from India but according to Shashi Tharoor, almost every Indian small business (people doing housework, ironing clothes, taxis, etc) all have a cell phone that people call them on to take orders. (Very interesting TED talk where this came from is
here it is well worth your time to watch). If you are taking orders with the phone, why not take payment as well and avoid the risk of carrying money around as well as the hassle of making change. You could even make it so the cell phone the business owner is carrying only carries his "recieve account number" with his main account being somewhere else so if someone tried to steal his phone they could not transfer the money out.
I could see something like the ability to make/take payments via two cell phones held by people who are face to face exchanging goods/services in person being a huge thing in this kind of Indian exchange (or anywhere else for that matter). This could be the thing that really leaps bitcoin into widespread use.
-Buck
