Depends on many things...for instance:
* If you are using this to charge mobile devices--assuming you mean via a USB connection, then why does it need to be "smart"? Just supply 5 Volts at up to 500ma. The smarts are in the phone.
If it does need to be "smart" [i.e. able to detect when the battery is fully charged and roll back to a trickle charge, that sort of thing?], then:
* First of all, do you have any experience with software design and implementation?
* What kind of power can your windmill deliver?
* What kind of battery technologies do you anticipate charging with this device (typically, it's Li-Ion, but your stipulation that it need be _smart_, suggests that you might want it to handle different technologies).
