BigBiss has just released a new solution, however, which they call a “semi-tethered” jailbreak. Using the new jailbreak will allow you to reboot your device on the go, but will only allow you to use the phone, send & receive text messages, and use some of the built-in apps (but not Mobile Safari).
Once you can get back to a computer, you simply need to re-run the latest version of redsn0w to restore your device to full functionality. The “semi-tethered” jailbreak works as a downloadable add-on available through Cydia. The package is available now, but be sure to read the original post at BigBoss carefully before proceeding.