remote access via cell modem

I have a a system which is comprised of a GE 90-30 374 CPU and two PC computers all communicating to each other via ethernet. I would like to be able to access this network remotely. My only option looks to be a wireless system (i.e., cellular modem?). Has any one had success in doing this and if so whose modem did you use (also if u happen to know cost that would be helpful)? The client is willing to pay for the hardware and monthly expense

I'm exploring using WebPort, they make a cell/ethernet version and ethernet only version. Seems easier then other solution out there.

http://www.spectrumcontrols.com/webport.htm

We've used a bunch of Cradlepoint CBR400s. The are pretty much a one port Ethernet router with a USB modem port the supports IPSEC VPNs. Support is very friendly and helpful.
http://www.cradlepoint.com/products/machine-to-machine-routers/cbr400-compact-broadband-router

I have been using the webport from spectrum controls for about a year now. Simple to set up and use. No complaints so far.