Only crazy people check valuables - especially in the USA
London, and the 'tunnels' used to be the prime baggage theft site for baggage theft, but now the WHOLE of the USA is on the list.
I always carry my goodies on my person as carry-on. If important, although less valuable, I put them in netted, as from Pac-Saf, which are securely attached to the bag. They permit inspection yet remain secure.
X-ray theft is also prevalent and I use the security cable from my laptop, looped through my jacket and other stuff, to prevent theft. Waiting, as in holding back, to ensure the X-ray channel is clear also helps prevent 'accidental' theft.
Most every flight I make requires a hand-job so previous passengers have usually cleared by the time my first carry-on has been X-rayed.
I also carry plenty of 'baggies' and make a point of packing my pocket items in them, before heading off for check-in. Even in a tray, stuff in bags is harder to steal.
Another distraction, during which thefts can occur, which can be avoided are metal belt buckles - I now only use inelegant plastic web buckles along with web belts and they NEVER trigger the X-ray. The only challenge is when a stupid security type says 'remove your belt' for I cannot remove my belt without taking my pants off!