zSMS is a handy application which was written in order to allow a PocketPC (Windows Mobile 5.0 based) to send SMS messages through a Bluetooth cell phone. The current version enables you to send SMS to one of your mobile contacts or to enter the destination phone number manually. Please note that the Bluetooth device must be paired through the PDA's Bluetooth interface beforehand. The message is then sent to the mobile phone through Bluetooth sockets, using AT commands. The message content is currently sent as-is (the phone number, however, is stripped of non-digits. Be aware that, depending on your cellular plan, you may have to pay for sent messages.
To install zSMS, just download the CAB file, copy it to your mobile device and launch it using File Explorer. On the first launch, you will be prompted to select your Bluetooth phone from the list of paired devices.