Intelligent communication over internet

Is it possible to create a Windows service to run on Windows Mobile 2003 that repeatedly checks for a GPRS signal (which is used to access the internet and thence to a server), and executes a transfer of messages (or files or whatever) - which have been created by a client application - when it finds that signal?
What are the performance implications?
Is there a more obvious solution to the occasionally-connected / message queing problem?

And what about triggered transmission of data by XML from the central server to the devices?

PS. MSMQ 3.0 is not an option