A Cisco 891 fits the bill but isn't cheap and is probably overkill. You might find a more cost effective solution with a router or firewall that allows you to add a 3G/4G card for cellular failover.

When you sign a contract with an internet provider, they'll typically send you a modem and a router in the mail. But which is which? And how are they different? A modem and a router work in tandem ...

http://www.zyxel.com/product/dsl/p642s.htm<BR><BR>View image: http://www.zyxel.com/img/product/dsl/p642_m.jpg <BR><BR>It's a "high-end" DSL modem, with a built in ...