Droid48

Back in the time when I was studying engineering, I saved money from what I was working on to buy a hp48gx calculator. They are awesome units. They use reverse polish notation for normal calculation and they are programmable using RPL(reverse polish notation, similar to lisp. Powerful language). In short, the calculator was stolen by somebody in the university when I was about to graduate. I never bought a replacement, but last week I found an Android app called Droid48 which comes from an open source project. If you have the time and previously used an hp48, try it out. It's awesome.