Hardware options

PC Card Adapter (pcmcia or cardbus)

CompactFlash

serial-cable to the good ole cellphone (either directly rs232 or attached to usb)

In the future possible:

USB attached modems (Vodafone just brought out a UMTS/HSDPA modem, not yet clear wether it works with OpenBSD or not)

PCI Express Mini Card (there are PCI Express Mini Card UMTS modules from Option and Sierra Wireless, to be found in IBM X60)

bluetooth? who hacks up our bt stack to add rfcomm stuff? ;)