These are not "generators" in the sense that you're turning mechanical energy into electicity. These "indoor generators" are just large batteries with a power inverter. Xantrex makes a few of these, and you see them advertised in various catalogs. They have a limited run life, limited capacity and need to be recharged over a realtively long period of time. They are best for lighting and least effective for loads like a refridgerator or freezer.

The model most widely seen is this one:
http://www.xantrex.com/web/id/63/p/1/pt/5/product.asp