I got an ap for my phone. I saw a few for $$ but I went with a free one for now (it's called C:Geo). It does pretty well.
I was able to find one with the boys just now, and got stuck on two others. I'm curious just how "micro" the micro finds are! I have a feeling I was super close, but I never found either one!
But the one we did find was awesome - it was a trading one, so the boys each traded for a treasure and are beaming from the fun of it!