My guess is that some high ranking Bandai executive let his brain damaged pet monkey come up with ideas for new products. The process involved the monkey flinging poop at the walls and whatever the resulting poop smear resembles that's what they make. This particular poop smear resulted in the Tech Pet you see before you.
I don't think the ideas are thought of randomly. Basically, Tamagotchi has a bad reputation, so they got rid of Tamagotchi and started again with a new virtual pet, which is probably almost entirely copied from Tamagotchi but with a new appearance and the involvement of a phone.
My guess is that, even though Tamagotchi is not seen as "cool" for older children or teenagers, young children couldn't get them either because of their parents reading about research that video games are unhealthy. But for some reason, parents let their children play non-educational, pointless games on iPhones but won't buy them a virtual pet, which can help teach responsibility. Also, the fact that this virtual pet looks more physical and like other toys, parents and children will see it as more of a toy than an electronic device, meaning more young children will end up using one.
I do think some thought has gone into this TechPet and it would be a nice virtual pet if it did not require a phone. An addition to the virtual pet genre - yes. But a replacement for the thing that started the virtual pet genre - no.