I've done SixNet modems, hooking the machine up to the DMZ port, port forwarding, Hamachi, fully loaded service laptop running VNC stashed in the panel, and e.WON. Of those, I recommend the service laptop route for unreliable internet areas and e.WON for everywhere else (if the connection drops, the service laptop will finish its transfer).
My old company got to a point that if you wouldn't buy an e.WON, they put in the contract that you would cover all travel and be billed at 110% normal service rate. If you didn't have cable or fiber internet, they also pushed a service laptop and the maintenance edition of the programming software.