I was given the Thumby as a surprise gift recently and I LOVE it! Yes, for 99% of people it's a silly novelty, but as someone who loves the Game Boy and making hobby games it's perfect for me!

I did a short review here. :)

https://www.youtube.com/watch?v=dzz4pJ0qXPw

EDIT: To clarify, the Thumby doesn't play Game Boy games, I just love small retro style portable consoles.