In high school, I used to print images, draw grids over them and carry them around in my sketch book. Now, I have my smartphone with me all the time and am almost never near a cheap and easy printer. Needless to say, I usually use my phone to find art projects or inspiration images.
Is there a software or website that can quickly draw a grid (of my chosen size) over an image on my smartphone that can be saved to my device? It would make my art projects and sketching from a photo a lot easier.