There is no application that can truly inform you about bus hours in Istanbul. Therefore I thought I should build mine. I simply get the data from IETT‘s content (I wish they had API) by using regular expression methods. This is sure a web application and I used iWebKit for the interface and PHP for the background.
The application’s interface is currently in Turkish. Simply you write the code of the bus line into the box and optionally select arrival/departure options. Then the application gets the list of whole bus stops and timetables for you. The information is always up to date and it’s always free.
You can try the application here: http://www.rahmetli.info/iett/