EDIT: Score lowered - have to agree with Chris, often it just doesn't work. Does mainly what I want but room for improvement if the author is keen: 1. If GPS doesn't change (i.e. you haven't moved and perhaps if it can't get a lock) then a message is still posted but has the exact same timestamp as the previous message. 2. Basic Authentication support. 3. HTTP Header support.
May work for you. It looked like a good app but it only works sometimes.
Good app, does the job well