Ask HN: Fun DIY projects to do with a month free?

For the next month, I have essentially nothing to do, and I was interested in working on a project, preferably one that ties together engineering and coding. I'm a competent coder, but only have a little electronics or engineering experience. There's a hard limit of $350 for the project, though the cheaper the better.

I was thinking of building and coding a magic mirror[1], but I'd love to hear any suggestions you have!

[1]: http://michaelteeuw.nl/tagged/magicmirror