I ran across this on Twitter tonight and thought I'd share it with you guys. Let me be clear, I am not asking you or telling you to buy this app, just sharing in case you were interested in it (or even perhaps some of your younger siblings.)
DragonBox is a game that helps you learn Algebra and, apparently, it's also fun. (Who knew?) I haven't played it, only read about it, so your mileage may vary. But if you're looking for that perfect gift (or your parents are), it might be worth $2.99 (or might not).
Here are the links: iOS, Android, Mac. There's also apparently DragonBox+ with more equations for $5.99 (I won't link, but search for it if you're interested).