PiBox » Xeon

It should be easy to implement this by utilizing pidialer as the base and add an option to run it as the text message app. I just need to provide a command line option to call it in text message mode.

The problem is how to get a keyboard for typing the characters. I could create my own (which is probably desirable in the long run to make it look good) there is a simpler solution: use matchbox-keyboard as an embedded app. Matchbox-keyboard (which requires matchbox-fakekey and, probably, matchbox-lib) has an example of embedding the app in a GTK app. So then we just need to embed the keyboard in pidialer with a text field to display the message. The text message must be limited to characters and whatever the SMS message limit is, unless the SIM800L can split the text on its own into multiple messages.