iDongle is a new device that lets you to jailbreak your iPhone/iPod Touch or reboot it on the go. It is very easy to use -- just plug it in and wait. The only problem is that it supports only iPod Touch 2G/3G and 3.1.2 iPhone 3GS.
At the moment there is only a dozen of this devices, but the developer says he collects money at the moment to build up a full-fledged production.