Need WiFi really, really, urgently?

Dropzone has created IntelliEdge, a WLAN in a box; a Linux server, but with the unnecessary bits of Linux stripped of, for an extremely reliable (many more times than Windows) host for communications. It distributes Internet access by WiFi (802.11a, 802.11b, 802.11g, et al.) over a local area.

It connects back to the Internet by WiFi, WiMax, 3G cellular and other kinds of connections, and only needs 9W at 12VDC. There's a solar-power/battery option, and multiple can be solar powered.

Applications can be run on the server, with its own GPS, so you could mount one on a 4X4 doing SAR work, and let it not only provide data connectivity, but keep feeding map updates (e.g., showing which sectors have been searched) to wireless PDAs and notebooks.