very good topic,
i don't think any network will give free data connection at the moment.
GPRS EDGE* or latest highspeed HSDPA* (internet for mobile phones)
*not sure the availability in sl
if you have GPRS you can use internet on your PC too
insert you simcard with a PCMCIA card.
check the link here
http://www.kyocera-wireless.com/kr1-router/user-guides.htm
this is a wireless router for atleast 10 users (depends on gprs data plan).
you can use this router in your car or anywhere you get mobile phone signal. video and voice data such as CCTV IP CAMS (inside the car) can be supported via new HSDPA technolgy(newer than GPRS)
check the industrial version of same EDGE technology mobile wifi access point / router from CISCO. normaly use for trains and public transport survailance CCTV cameras.
http://www.cisco.com/en/US/products/hw/routers/ps272/tsd_products_support_series_home.html