We have the Progressive 50 amp portable. It's not the cheap one. I believe it is $431, but very well worth it.
We lock it, but have never really worried about theft. You can also have it hard wired in, but we like the portable unit because if you plug it in and find you have a bad pedestal, you can take the unit over to another site to check that pedestal and not your whole RV.
It has saves us twice. The last time was in our semi permanent site that we had been away from for only a month. When we came back it gave us an error message. The maintenance guy said "I hate those things, because they give false readings." Well, it turned out, it did not give a false reading and he had to replace the 50 amp circuit. This was on a pedestal that was less than one year old!