There are more and more products coming out to mount a phone to a telescope, bicycle, and riflescope. We've been working with different designs, too. Here are some of the things we've been doing.
The simplest design (KISS) is simply modifying a hands-free mount for our older Droid. Not only are older smartphones available for cheap, so are their accessories. We got this car mount for < $4 on ebay.
We simply drilled a hole to expose the camera lense, then took off the adjustable arm from the suction mount and connected it to an aluminum picatinny rail adapter for a flashlight. Easy peasy.
For use on a carbine or rifle, the simple design wasn't enough to put the phone out of the way of the action. So, we cut off the base of the suction cup, and mounted it to the picatinny rail. Now, with the adjustable arm, it puts it out of the way and right where we need it on an AR or AK platform.
here) and it is a blast.
A mount for a rifle has been more difficult. The biggest problem isn't mechanical, it is dealing with an existing scopes parallax. Parallax is the focus of the scope - when you are eyeballing through the scope there appears to be a small, dark "window" for viewing that changes in size as you move your eye around. Positioning the smartphone just right to view through the existing scope is alittle tricky, but not too bad.
Our first design was basically a PVC pipe cap with the phone's mount connected to it. This worked, but didn't give enough range along the scope's axis to adjust for parallax.
There is a demo on the Smartphone's page at Google Play (here)
I'm sure we'll see lots of different designs and products out soon...