I'm trying to use the re-usable glue which is used to stick telemark skins (for climbing uphill in snow) to telemark skins. It's a very tenacious glue which can work when wet, and covered in pine needles and dirt. The idea is to make a spectrometer attachment which can be stuck and unstuck easily. We could even use a piece of the skin glue protection sheet which comes with skins:

The glue irons on (maybe temperature makes it extra sticky?) so I may try that tonight. It didn't stick super well to my curved-back Android phone (at first it worked, but it started to work loose as I waved it around and such) but I'm also going to test it on an iPhone. Mathew Lippincott also persuaded me to buy Glue Dots, which should be arriving soon, so I'll try that too.

Update:

Tried more glues, adhesives, etc. Telemark skin glue worked super well on the iPhone:

But not as well on the curved Android back. Removable adhesive strips did work, even holding over a pound of aluminum:

However, the best was this heavy-duty velcro, which stuck and came off without a trace:

Turns out it doesn't seem to make a big difference if there is some space for light leaks on the sides. Here's a great photo of the junction. It's not the cleanest, most elegant thing ever but it is pretty nice, and doesn't damage your phone at all. Perhaps we could ship a few different options and people could choose the best for them.

Still waiting for the Glue Dots to arrive though.