Location app to inject GPS data into photos

I take a lot of photos with a sub SLR camera, the only thing it is missing is a GPS.
What I end up doing is trying to remember where I was when I took the shot and manually entering that in the JPEGs meta data (EXIF). This is obviously prone to error and time consuming. I don't want to buy a new camera with a built in GPS or bolt an extermal GPS unot to it.

I was wondering if there was an app on Android that would track where you were and store this next to a time stamp. Then if the clock on my camera was in sync with the phone I could know where I was by looking at the time stamp on the image and matching up to the location at that time on my phone.

The perfect solution would be for some way of automatically getting a program to inject the location data into the photos meta data.

Does this exist?

Many thanks