tcwozere, looked at the link you gave, and it looks good, part from it doesnt look very compact therefore surely a thief could just remove it, put it on a lorry and have you on a james bond style wild goose chase, ahha

so maybe if there is a compact version!
how to secure a boat on trailer is virtually impossible as if they want it they will get it, there are ways around most security systems, like the hitch lock, the trailer could be bound instead to a towbar, so i have thought of ridiculous measures haha, take one wheel off, clamp the other, hitch lock, and chain the whole trailer to a metal hoopp embedded in concrete, haha. a small chip which could be hidden would be great, note to inventors!