Thanks for getting back to me on this.
I'm running an iPhone 4S. And that's exactly what I do - double click to get to the camera and take the photo then double click to get back to Cachly. The Cachly screen appears as before but the distance countdown is frozen and after a few seconds it sort of reboots itself and goes into Live mode. I also run an Ordnance Survey map app at the same time and there are no problems with this interfering with Cachly - or vice versa.