Maxim makes quite a few iButton devices. Some of these don't require batteries, but several do. Unfortunately when an iButton battery dies, the data stored in the memory is lost. The only exception to this is the DS1925. Although it has a battery, data gets stored in non-volatile memory. The power to read the DS1925's memory does not come through the parasite-powered circuitry of the 1-Wire front end but through the strong pullup delivering power from the PC adapter.
