Fido doesn't "support" anything but Windows laptops connecting to phones. But
if your phone supports the right standard for AT commands, then any device
with a serial port can talk to your phone. (am hoping to test that theory soon).

Essentially, your phone acts as a PPP server. So your PDA thinks it is dialing
up some ISP but it is in fact "dialing" to your phone.

http://WEBAPP.ETSI.ORG/exchangefolder/ts_100916v070500p.pdf  provides the AT
command standards for GSM phones.

Your GPRS phone has a couple of configurations for data access. Each points to
an APN (think of a router). So the WAP profile points to a box on the Fido
network which handles the WAP protocol. And the GPRS profile points to an APN
which handles raw TCPIP connections to the internet.

So the AT command you send needs to specify which profile/APN you need to use.

I am not sure about the DNS servers though. With PPP, one normally has to
hardcode them in one's configuration, and if so, Fido should have those
documented somewhere because even on Windwos you'd have to specify them.

Also, Fido does offer a HTTP proxy which will compress web pages (images
especially) to reduce the GPRS costs. I think it is rapido.fido.ca:8080

The WAp service already acts as a proxy which compiles WML pages and scripts,
and compresses images into the WBMP format on the fly, handles cookies on your
behalf (cookies are stored at Fido, not on your phone), as well as being able
to do some coversion of HTML into wml.