The watch is impressively thin and compact for a DIY build, and has a host of useful functions without going overboard. We’ve seen other DIY builds in this space, too – such as this ESP8266 ...

This 100-page guide lists out 175+ kits that you can build yourself or with your kids. Like the Ivory Soap tagline from years ago, "99 and 44/100 percent" of kits are pure and safe.