At Freakonomics: Is Tipping Really So Hard? Apparently the iPhone App Store features a rather large number of "tip calculators".
Is it really so hard to multiply (approximately) by .15? (Or some other number; I don't wish to debate the "correct" tipping percentage here.) I've always figured that the hard part of tipping is not the multiplication, but the knowing who to tip. For example, do you tip food delivery people? I do on those rare occasions that I get food delivered; they bring the food to your house, which you could argue is more work than bringing it to your table in the restaurant! Plus a lot of them pay for their own gas. But in reality, I don't get food delivered, because I know I should tip, but I don't want to. Do you see how this gets complicated?
However, I am better than average at math and worse than average at "social skills", so I hesitate to generalize from my experience.
But as some people have pointed out there, this gives you an excuse to pull out your iPhone. And it's also the case that it's basically the simplest application one could write that actually does something useful.
A bill-splitting calculator I can see being useful, in cases where the amount of food people ordered varies enough that people aren't willing to split it equally; although I personally would never be in a party that would need it, because I can do the arithmetic. (And yes, my friends know this, so on occasion they'll ask me how much they should pay instead of figuring it out themselves.) But I can't eat with everybody! But even a bill-splitting calculator suffers from the fact that the hard part of splitting the bill is not the math, it's remembering who ordered what.