A questionably legal but terrific calculator is any TI-8x emulator for Android. I think as long as your own a real TI-8x and extract the ROM yourself, you can legally use the emulator. One of the emulators is called "Andie Graph".
Bit pricy but it somewhat easier to navigate than HP-48. Though it has limited RPN support...
[0] https://play.google.com/store/apps/details?id=com.hp.primeca...
Alas, nowadays it's overkill. A bit like a Mack truck, which you use to drive 300 metres down the road to buy a pack of cigarettes.
It's still one of my favorite gadgets, though.
On a serious note, you have to admit that the familiarity of the calculator helps. I don't know how much you're crunching numbers for complex calculations, but trying to get them to work on Wolfram Alpha or some other web calculator can be near impossible.