Hi
I want to create anew device that can be detected automatically as a keyboard or mouse .
I understand that one of the boards with this functionality is Leonardo ,.
The questions are there any other Arduino boards that have this functionality , and if there are any smaller ones the the Leonardo ?
There are clones which are smaller, the best none clone imho is from freetronics, thumb size complete with speaker and rgb it's ready to go and controls keyboard and mouse.
I used it at tafe to login my username and password automatically, I'll use nfc next time
The due has HID as well and the yun (which is a leonardo+ a linux running openwrt).
have you looked at the teensy? There are couple of them and they all have HID? https://www.pjrc.com/teensy/
The teensy3.1 (say due ++ in a small package) is currently on sale for 17$ Teensy 3.2 - Purple OSH Park Edition | OSH Park