I have a Smart roaming sim card from Phils (bought as part of a pack of 3) and keep it in my cheapo basic nokia phone, it costs my wife 1 peso to sms me. I then use an Orange Camel PAYG sim which I then can call her back and chat. I still use my contract Orange phone to sms her back, which is probably not such a good way to do it, but I still do anyway.
Alternatively, get her a smart phone with yahoo messenger on it and she can text talk for free on the internet. But like Steve says, there are so many ways that we all do it, take your pick.
