Using ATTiny85 as a USB HID Mouse Our project involves using an arduino compatible microcontroller to control a mouse on a computer with an accelerometer and flex sensor. We had narrowed down to the ATTiny85 due to its small size.

We found a particular tutorial on the Adafruit tutorial  website, using the Adafruit Pro Trinket using the same ATTiny85. 

Is there a reason to believe that this won't work?

Also, does anyone have suggestions as to which board to use apart from Micro as it isn't too available here?
Due to the lack of USB-Support of the ATtiny85 you will be forced to use something like V-USB as the tutorial does. This might have implications when you are targeting a commercial product.

Personally I'd suggest using the ATmega32u4. It has USB build right in.

But basically I don't see any reasons why it should not work.