I was quite surprised to see that you can send SMS from GMail to Dialog and Mobitel numbers in Sri Lanka. Tested it out and it works. Sent to myself, but you can have a conversation with someone on the phone, all from GTalk. Since I got an Android phone, that’s been the most useful app, and now it’s extended its reach even further.
How it works is that you get 50 SMS to start. Each time someone replies to an SMS from you, you get a credit of five. Thus, if you use the service as it’s intended (conversation) you should always have credit. For the phone companies, this means that there’s an incentive built in for them to get paid. Kinda cool. The SMS credit policy is explained in more detail here.
One tip you may not know is that, for Dialog at least you can send email to phones already (firstname.lastname@example.org). I think this just tells you that you’ve got a mail and gives you an excerpt. Not that useful. With Google SMS, you can enter a number (I had to put a zero first) and send messages direct.
Google already has impressive voice integration with US networks, but it’s definitely cool that they’ve spread this SMS feature to so many countries. Most young people I know in Sri Lanka are permanently on low credit or giving ring-cuts, so this is another option.
Oh, and speak of the devil, I just got an SMS from Dialog itself, linking to their page on the service.