No to the magnet, and the reader needs to be within a close distance to the chip, to "see" it.

Just imagine the loops you walk through to enter and leave a retail store.

So no they aren't going to drive down the street and read how many chips you have in your collection. Yes they will have scanners (actually loops) at the employee entrances and exits.

I suppose they could have them at the doors of the casino, but it's getting a little bit complicated, and I don't know the range of a microchip...chip.

Let me guess it's about three feet or less. Someone can correct me if they are different than other devices of this type.

Think of the little foil labels in library books. They are never changed and that's why they pass them around the back of the sensor. If you try to walk IN with a book, it will set it off, and of course, walking out would be the obvious reason for having them.