About the size of a deck of playing cards, the Jetpack can support up to 10 different Wi-Fi connections over the 4G LTE connection (over 3G it drops to only five supported devices). This lets you easily share the connection with co-workers or family members while traveling -- for example, in locations where Wi-Fi might be available, but expensive (hotel rooms) or with bad service (bad hotel rooms).

IN PICTURES:

The Jetpack powers up quite easily, and if 4G LTE service is available, it will quickly connect and makes itself available to users. Connecting to the Jetpack is done via WPA2, so guard the unit's password carefully (you can change it, of course, if you want).

The device has a very nice graphical display on the top, giving you information like how many bars of service you have, whether you're connected via 4G or 3G, how many users are currently connected, and battery life indicator. My only complaint is that to save power the display goes dark after a brief period -- if you want to constantly monitor your connection, you have to keep pressing the power button. Another warning -- while the speeds are great with 4G LTE, you have to be careful to make sure you don't go over your allotted data allowances.

Now for the train test. Amtrak does offer its customers free Wi-Fi access, but the connection from the Wi-Fi to the Internet isn't 4G, as far as I could tell.