In Tokyo, many people use these little gadgets.
It is a 3G data modem coupled with a little WiFi router.
You turn it on, put it in your pocket or bag. It creates a data connection via the 3G data sim card. Then it uses the built in WiFi router to create a WiFi network. Now you have your own personal WiFi network that goes with you. The battery lasts for 4 to 5 hours. It supports 5 computers/mobile devices. Many iPod Touch users like this device as they can connect to the internet from anywhere.