Crazyflie from http://www.bitcraze.se/ is also pretty cool. I own one myself, and I like it a lot. This is a tiny fully opensource quad which can be flown indoors. I think I'll add a camera like the post to make it FPV.

I'm wondering if it's feasible to use this cheap micro drones as a base to build an ardupilot.

Any experience about this ?

Some microdrones can be hacked to run custom builds from Multiwii code

https://github.com/silver13/h8mini-acro

https://dronegarageblog.wordpress.com/2016/01/06/eachine-h8-...