C3 Expo: Power for Your Notebook. $ From Your Pocket.

What if you could use your notebook for 24 hours and never connect to an electrical circuit? Electrovaya’s PowerPad 300 will let you do just that. The downside is that it costs $800. There are other PowerPad’s that cost less and offer less battery life.
As notebook computing prices decrease and as technology evolves, especially in the area of battery life, you might find less of a need for an external power supply.
On the other hand, for industries that find themselves more often than not AWAY from a power source, the PowerPad is an ideal solution. The longer lasting PowerPad’s understandably weigh more, so consider the added weight a deciding factor as well.
Electrovaya also sells a line of TabletPCs.