The Yacht Router Micro from Locomarine is over 1000€ but promises to connect to wifis and GSM.
Digital Yacht offers routers with high gain Wifi antenna and GSM module.
The Yachtrouter 2 from B.I.S. promises connectivity to harbour Wifis and has two GSM modules.
This blog has no tests for these devices so far. Please provide some information if you have any.