Recorded angry dog is a good deterrent. I have Radio 4 or 5 chat shows going on in my garage if anyone walks near the side door and window or touches the metal up and over door. If they did get in the strobe lighting might make it hard to see much and the 2 cameras would film it all. I just cannot see why they are unable to keep burglars out. Bolts into the walls to hold doors and then there are some good ground anchors and chains around the wheels so they cannot push the bike. Plus chain them to each other and large objects in the garage like an anvil or lathe.
When i go away, i fit 17 chains and padlocks to lock up 4 bikes. Cables, chains and tie them all in to the bike lift and fixed floor chock. It would take an hour to get them all off while listening to the Archers on the radio.