1) What exactly is the GSM module? Is it just slot that accepts a cellular SIM card? Something else? I've been trying to read up on this and I don't completely understand what the "GSM module" is. Do I need to purchase a static IP to make it work? (I remember having to purchase two static IPs to make HiPers talk to eachother via AirLinks). 2) If I opt for a 5800 with a radio module instead of GSM module, can you still use it with a RTN via a bluetooth connection to a cell phone? 3) If you wanted to use the 5800 solely for RTN connections and maybe OPUS, would you opt for the GSM module or a radio module and blue tooth connection to cell phone (assuming that's possible)? Is it less expensive to use your "smart phone" data plan (via bluetooth) than to have an additional dedicated cell-modem data plan?