If you're looking for a physical remote shutter release (not by software means) consider the 1020 camera grip which has a shutter button that is interfaced with the phone via USB. I think someone should be able to figure out a remote release/shutter release cable for Lumias with a connection via the micro USB port. It has to be either via a contact closure or voltage signal to the USB lines...
Someone should try connecting the 1020 camera grip's USB to a 92x phone and try if it works...
I'm absolutely looking for one. Are you saying the button on the camera grip works via usb? If that's the case, it should be easily rigged with some tender loving soldering...
You can use voice command to take a photo / video. I believe it was a Nokia video where a guy was hitting baseballs and taking pictures and video with voice command. Never used it myself so I cannot comment any further than that.
Oh yeah, there are a couple of solutions for iOS. Wish they could just enable recording via the nokia BT headset-controls. You know: start the nokia procam, select video/stills, press play on the bluetooth remote to start recording/take pics...
There is an app called Tapshoot which allows you to use another windows phone to operate the camera and you can use the screen as a viewer as well. Pick up a cheap Lumia 520 to use as your "remote" and away you go...