I have a shot gun cartridge trip mine wired through my plastic garage roof, it fires a blank 12gauge cartridge, should deter them along with 5 different locks and ground anchors both doors alarmed and pir sensor and wifi cctv covering garage and front of house which offloads footage to cloud.
1 x 40quid easy n foscam rip off copy cctv camera from amazon, used inside garage and 1 x EyeSpy247 external camera £180. I use vitamin d software and have an old laptop acting as a dvr, but also have it linked to a Microsoft SkyDrive account with 7gb of free storage, any movements in the covered areas also means an email turns up with a picture attached.
I have to break in to telecoms cabins as part of my job
So I have made as difficult as I can, from the prospective of If I was going to break in how would I do it, isn’t impossible but if they did nick my bikes without me knowing I’d have a grudging respect for them.