Nobody ever accused me of having good intel, but the Asus eeePC line seemed to be up there in battery life. I have an eeePC 1005 10" netbook, but I use it as a Linux box even though it came with Windows 7 Starter. I haven't verified their claims on battery life, but they had options:
10.5hrs, 6-Cell 63Wh Li-ion Battery
8.5 hrs, 6-Cell 48Wh Li-ion Battery
4 hrs, 3-Cell 23Wh Li-ion Battery
Unfortunately, the charger output voltage is 19 volts so it won't charge directly from a car battery, but 12 volt car chargers are available.
I have not used mine with any of the digital modes yet, but I believe it has the horsepower to handle them. It runs Lubuntu nicely. Newer models have more powerful processors but the 1005 is relatively cheap - around $100 to $150 on eBay depending on configuration. Some of the newer 1005s had a faster processor than the original ones, so that is something to pay attention to.
Wally