You know those rubber bands they supply to attach your amp to your phone / player? Crap right? This is a Fiio E18 being securely attached (whilst still being removable) to my Otterbox Commuter cased Samsung GN3. The case is important for reasons I explain later on.
Here's a couple of photos to show the material I used to connect my Fiio E18 to my phone. This 'tape' is excellent. It looks like Velcro but is much stronger than that. Remember stickle bricks?
Below is a link to the precise grade of tape I bought. Someone else here bought the grade above and it was so secure it was incredibly difficult to separate the components once attached. This link is to the same tape but one grade below. It's so strong I'd have no problems trusting it with three times the weight used here. This is an Amazon link but hardware stores and builders merchants sometimes sell it too.
http://www.amazon.co.uk/gp/product/B004AQFBE0/ref=oh_details_o03_s00_i00?ie=UTF8&psc=1
Just cut two strips to fit both your amp and your phone. They don't have to be millimetre perfect. These are about 4" long but this stuff is so secure 2" would be enough.
Do make sure you apply the strips right down the middle of the devices. Anything out here (even 1mm) will make you look like an incompetent ass who shouldn't be allowed near a kettle.
This photo's only here so you can see my deep Scottish tan. Cool huh?
You need to be careful at this part. You need to squeeze the two components together and the force required seems excessive. It's fine as long as make sure to spread the load right across your screen. Screen protectors are useful here. Do one end and the rest will just fall into place. If I had a third hand there would be photo of the big squeeze here. Sorry. Once the two pieces are together it will look snug and feel like one solid component. Or a bomb.
Superfluous image of sexy man things. Calm down at the back there.
Taking it apart requires a lot of force but it does come apart. I've had mines apart loads of times with no damage to anything. I'd really advise fitting a secure case to your phone. I use an Otterbox Commuter case for my phone and love it. You don't have to use an Otterbox but whatever you do use make sure it's secure and not one of those daft rubber bumper efforts. When the amp needs charged just run caseless. If you apply the tape to a bare phone it means your phone is out of action when you're charging the amp. An amp charge takes up to 4 hours.
I hope that's of some use to people. If you ****it up it's your responsibility but it works a treat and a million times better than elastic bands on a touchscreen.