My Time Capsule is not connected to my router - it is just added into my wireless network and acts, as you describe, as a wireless backup device. Set it to 'extend a wireless network'. Like Hyph, it helps extend the existing wireless network, which is useful in an old stone cottage, and also I have a printer connected to it via usb which makes the printer available as a wireless printer on the network. It could however, given a suitable power source, be hidden away in the loft or be bricked up in a wall somewhere.
I think I responded before, but like you I am a bit paranoid about losing the laptop and the TC in the same burglary, so I also frequently backup to a separate portable hard drive, which I try to keep in a separate location to the TC. Time Machine will allow you to back up to multiple drives - the TC backs up automatically in the background and the other drive backs up manually whenever I hook it up.
Last edited by Background Noise; 23rd Mar 2016 at 10:10.