I just had a request from a math teacher for something she could use in place of a physical graphing calculator in class. I do love me some Desmos, but it's not always the right choice when you're trying to do something more algebraic (like matrices). I did a little googling and found Meta Calculator. I only played with it for a few minutes, but it looks like it could be a nice alternative to the TI-whatever when the kids don't have one handy.
Some screenshots from their four calculators:
There's an iPhone and iPad app available, but I also want to test the calculator to make sure it works on Chromebooks (I can't see why it wouldn't) and other types of tablets. But for now, it's looking good!