You want a laptop. If you want something smaller, you want a netbook. If you want something smaller still, without a keyboard, and without flash, you want an iPad.

You can get any of those with mobile/wireless data (either via USB dongle or sim slot) - the netbooks and iPad will give you 5-10 hours battery life easy. Me, personally, I love my netbook.

If you want something even smaller then that, you don't want the best internet browsing experience.

If you want the best handheld linux device with physical keyboard and integrated GSM data/voice, and passable internet browsing experience, you want an n900.

What did you want again?