When many people think about wireless networks they're thinking about Wireless LANs. An 802.11b typically has a range of about 100-300 feet and is used to extend an existing wired LAN to wireless clients.
I have many clients that use 802.11b, 802.11a, lasers and other similar technologies to connect geographically separate sites up to 40km away and provide speeds from 1 Mbps up to 2 Gbps.
Depending on your requirements (which sound quite minimal if you're just talking about a couple of cameras) and whether or not you have line of site between buildings, a wireless bridge may be a viable alternative.
If that's not possible then you're probably left with only one option – the local cellular network. Australian telecommunications carriers have recently released their 3G networks (IP-based, high speed cellular networks). Currently these are quite expensive, however that might not be the case in other countries. If this is the option of choice then each camera will probably required a cellular-network adapter in order to communicate across the Internet.
If what I've said makes sense then I would recommend talking to a local wireless specialist (as opposed to a standard networking company.) They should be able to provide some prices for the most viable option.
This was first published in August 2003