This one, listed on the Second Life Marketplace, appears to use the same media-hack to identify the IP address of other users.
The creator suggests that this doesn’t violate the terms-of-service, since it does not send data to any person other than you, nor does it show you the data that it collects.
All it does is tell you if account A who visits your land parcel, is the same as some other account B who visited your land parcel, based on whether they have the same IP address.
I presume that it is self-contained, requiring no external server.
It’s an interesting trick – and it might well side-step the letter of the Second Life terms of service.
Whether Linden Lab will actually allow it or not (it certainly has the freedom to block anything it pleases), is quite another question.