Skydeck used to offer a service that would keep your SMS messages from your phone backed up, but they are now focusing on offering what I’ll call “social caller id” and they have rebranded at Mr. Number. MIQ offers this SMS backup along with a few other nice features. You can send messages through your phone from your computer keyboard, see a list of all your calls and add notes to them and backup the media on your phone all over the air.
I heard about a guy who had someone else install MIQ on his phone without his knowledge. Late at night the perpetrator would log into MIQ and send out inappropriate text messages to everyone the victim knew. It came from his phone, but he had no idea how it was happening.