Excellent offline map and guide!
This was an excellent tool for my recent trip to Istanbul. Similar to having a handheld tourist map of the city, except it offers a much more detailed street map I believe courtesy of Google, as well as Underground map, and even ability to search for landmarks/restaurants/hotels/etc on the map. Also very helpful was the ability to open up Wikipedia pages of all the tourist sites all while offline. Great app!
Droyo about
Istanbul Travel Guide and Map