ProfJohnL said:
The only guaranteed permanent live wire will be direct from the battery.
As the Prof generally knows what he is talking about, I am sure he did not mean to imply a wire with no fuse in it.
In a caravan there will be a 12 volt fuse panel (NOT to be confused withthe 230 volt one) with the various fuses fed by the battery and the connections from the tow car, from which wires will go off to the various functions in the van. At least one of these fuses will be for auxiliary things like 12v lights etc upstream of their isolating switches. This is the point, separated from the battery by only a fuse, at which to take a feed off for a further auxiliary such as a tracker.
You do not want to be making a connection direct to the battery itself for all sorts of reasons , including the fact that the large battery connectors are not engineered for additional minor wires, and that the extra fuse you must add is likely to be "lost" unless you place it alongside the other existing fuses, in which case you might as well make use of the existing battery feed there.
Again, as the Prof said, if you are under the impression that a wire direct from the battery might be "too powerful" then you have a bit of a learning curve to climb before tackling this sort of job yourself.
And as others have said, a tracker really needs its own battery, recharged from the main battery, as any competent thief would disconnect the main battery entirely before towing it very far.