Developed by a couple of "mobile content companies" in Finland
is a Tamagotchi
-type virtual pet
that lives in your cell phone
The victim, errr, user interacts with it via SMS messages, (the application software is stored in part on a central server due to in-phone memory limitations). This also has the benefit of chalking up large profits for wireless service providers at the same time.
Kiepo can also interact with other virtual pets over the internet, taking part in dancing competitions and visiting the library, apparently.
Mercifully, Kiepo has yet to be taken up by any wireless carrier, but it's only a matter of time...