I'm also interested in using an indoor "pee box" and looking for recommendations from folks who have tried this solution. The PetZoom pet potty on Amazon (http://www.amazon.com/PetZoom-Park-Indoor-Potty-25-5/dp/B002ZHRTAK) looks workable.
Here's the situation. My male B is 14 years old and has started to need to pee late at night or in the middle of the night. He gets three 30-minute walks each day, so he has plenty of opportunities during the day to empty his bladder. (I think it's a general weakening of bladder muscles, as I hear that this happens with older dogs.) The only time that he is peeing indoors is, as I said, late at night. This has happened more regularly over the last month. I put a tarp down by the front door each night, covered by a sheet; he pees there, and nowhere else, and then goes back to sleep.
I'm continually washing the sheets, and I don't have a washer/dryer where I live, so I'm considering the indoor potty.
Any recommendations?