Is monopod (selfie stick) with headphone jack supported in Windows Phone, or are there workarounds?
It looks the default camera is not supported. (cannot capture with "volume up" button)
(in particular the Lumia 630 and Monopod model Z07-55)
AS far as I can tell it is currently not possible for developers to detect if the phone volume has changed - and therefore can't take a pcture then.
You could either look for Bluetooth remote controls that might be able to activate the shutter or you can make use of the self-timer in the Lumia Camera for now.