A device (the kickbee) developed by Corey Menscher and worn by a his pregnant wife sends a twitter to dad every time the baby kicks.
You can't buy one as it is a technology/art/media project.
Alternatively you can get twitter messages "from your baby" during your pregnancy at tweetlet. I imagine that it is like the information in the books that say something about every day, week or month of the pregnancy. Such as "I now weigh about one pound", or "My eyelids have finally grown in".