I didn't know what a strain gauge was, until I googled it some seconds ago. That's funny.
1. Terrorists can use everything to trigger bombs (even themselves)!!!
2. Less technologic materials can do the job, so why bother buying such a complicated electromechanical part?
So, as a conclusion: Stupid restrictions against a... strain gauge!! (hahaha) will not stop them on any way!!
PS: Instead, they jam the work of honest people
PS2: Same thing applies here, but against Isopropilic Alcohol. Great for cleaning wet electronic devices, paint stains... until a "#$%&@ terrorist had the great idea of using it on drug processing. Now is expensive as hell, and all orders are reported.