Home automation Controller/server needed
As I understand it, you're looking for a device which can monitor a serial port and send SMS messages.

The list of devices you gave are roughly in descending order of price, so I would guess that you want low cost.

Here are some ideas (substitute Arduino for your favourite microcontroller board):


Arduino ($30) + Cellular shield ($100)
Arduino ($30) + Telit GM862 ($100) (example)
Arduino ($30) + old mobile phone with data interface ($free?) (Arduino library)


If you have a broadband connection at the remote site:


Arduino ($30) + Ethernet shield ($46) (telnet example)