At this point in 2014, pretty much every digital device is also a calculator. Growing up, I always longed for a calculator watch. The idea of one now seems very quaint and very EIGHTIES.
Since the dawn of the digital calculator there has been a slight mistrust of them. As a classroom teacher, I can remember the big debate as to whether or not we would let elementary students use calculators in the classroom. In examining some of the current calculator apps available, I think that it is quite humorous to come across items like the DIGICUS (Digital Calculator + Abacus). http://retrocalculators.com/digicus.htm has a rather fascinating history of this device.
For quite a while now, Wolfram Alpha (http://www.wolframalpha.com) have been solving equations for us. The same is also true for the Google Search Bar. It is rather interesting to think of growing up in a time when the computer could have solved my Algebra homework. The problem that this brings up is that it is now more important than ever to go beyond just asking students to solve math problems. It is far more than just the procedure. We really need to be asking them to DO SOMETHING with the math.
More recently, apps like MyScript Calculator have taken this even further. Rather than entering in numbers using buttons, one can simply write the problem to be solved.