I elected to follow the caravan fraternity on the subject of wheelclamps.
They have independent ratings and awards for security locks etc and I would hazard a guess that more caravans are nicked or attempted to be nicked than boat trailers every year, so felt comfortable following their recommendations. It seems like the Milenco units are well reviewed and approved by insurance companies.
As we all know, any security device you can think of for a trailer, can be hacked, ground, beaten, or smashed off by someone who is determined to do it, and even the security bolts for a Bradley locking hitch can be ground off in a short time, and a new hitch bolted on. We are only talking deterrent value, and something that insurance companies approve, so I say do some research before buying, but realise the limitations.
Trailer Guy on here, could no doubt offer some useful advice on approved/fit for purpose trailer safety devices.