Somewhere online, there was a page on how to make a hack adapter that did the same thing as the Keeler device ($299, IIRC for a one-piece molded plastic holder) from a cheap iphone case and things like DVD spindle spacers and plastic caps from shaving cream cans. All-in, it took about $12 in parts and glue. It was made to fit over the eyepiece of a Haag Streit/Topcon-clone slit lamp. I imagine you could make something similar for the Google phone.