Router with a data card slot?

Hey,

Have a question i hope you guys can help me with. My company has 2 sites that are currently linked with a leased line Site A and Site B. Site A is our main base and has the internet connection and site B is connected to Site B via a leased line.

Site A's network contains the databases etc the guys in B work on day to day and it is critical the link is maintained. Site B is in an area with no wireless or broadband coverage unfortunately so the leased line is the only link to the world.

If the line goes down site B is paralyzed - I want to have some redundancy set up here and i was wondering what kind of gear is available to help me. I was thinking of perhaps some kind of router with a data pcmcia card so it can use the mobile phone network for a connection but i cant seem to find anything of this nature.

Anyone got any ideas ?