It would be nice to have a simple program such as Babytype aimed at toddlers.
These programs (I think there are several) are aimed at toddlers who like to hit keys and typically make a sound and show a picture for each key, along with some device so that the toddler cannot exit the program or get into another the parent does not want touched. This lets the baby play "computer" just like mom or dad without doing any damage.
They seem ideal for promotion this way since if used they are likely to be used a lot and friends told about them. Those without toddler's are unlikey to download one, but later after the baby may remember the program exists.
Many parents would pay a small sum for such a program for their kid, and on learning of it from a giveaway user would buy it.
Such programs are simple to program (assign a cute picture and sound to each key, and put an exit procedure on that requires reading or a skill a toddler will not have). One of the game developers that works with giveawayof the day might want to undertake the project and would probably recover the cost in sales in a few months.
Those with babies or toddlers download the program free (many stay at home moms probably frequent the site). The parent put it on to entertain the baby when there is a visitor. The vistor notes the program and how happy the baby is banging at the keys and goes home and pay five to twenty dollars for the program.
Other parents get told about the program.
A couple of bells and whistles could be added to permit a parent to add a picture for certain keys (say of the baby) or possibly a simple music clip for certain keys.
While such a game is easy to program, it is just complicated enough (with finding the bright patterns and right sounds) that few parents would bother (even among those who know how to write a macro).