You could get a zoom h1, very cheap and
Audio is same quality as the h4. http://www.youtube.com/watch?v=8Fn6-WWJFeA
A lavalier (the interviewd person carry the
Zoom behind at belt level.
Got another mike in your cam like a rhode,
And you're good to go on the cheap.
Or even got 2 zoom h1, One on the talent with lavalier,
One on your cam shoe Or tripod that takes the
Surrounding, and a third mike plugged on your cam.
It's as easy to sync 2 sources Or 20.
The only thing is that you'll have to launch the ext
Mikes previously to the take, and do so to stop recording
Because there aren't electricaly connected
With your cam.
If you got a mike plugged in cam, you don't
Even need a slate to sync in post, nor any
Third-party app. But using
A slate is always reliable 100% and easy.
Ps: avoid those tablets gadgets as slates.
A simple good old manual clapperboard.