Cool! I'm still looking for a picture. I'll post when I find it but thinking about this more I know there are a ton of toys like this made. Most are for older kids and are priced at about $20-80.
Look up circuit station kids science and you should get an idea of the kits.
Here are some links I found:
Yeah around three they should be able to do it with adult supervision but it's still a bit of a toss up on if they are going to put the small parts in their mouth. I can't find the a good photo of the big one at my local children museum. It's going to drive me crazy. I'll probably just have to take a picture next time I go in.