It has been long time that I recommended any widget. Recently I checked the version of any updated widget. Here is one called PEMDAS, I like the interface changed in version 1.1. I found I prefer to type the whole formula all the time instead of press the keys in Calculator or similar application. It’s so simple! You can even use ANS to take the next step of calculation. Also it will auto cache the result of each step! I’m sure science student would love it the most! Though, it provides scientific functions but I think housewife would like it as well. It’s easy to use.