TamagoChu

Released at the end of January 2007.

These little guys are nice and basic. Just un-tab it, set the date and time, then you get to choose one of three different characters on each.
There's no discipline or feeding. There are 3 buttons across the bottom. The first shows your characters name, then the name and picture of the tamago-chu boyfriend/girlfriend you've connected with.

Apparently you could run more than one and determine if the different tamago-chus will like/mate with ones from a different set. You basically just connect them when you want, and if they call/miss their partner. The more you connect the greater their relationship will be.  Simple, yet really nice.