I had thought about the Wish List feature almost exactly as you describe with the addition of a Lending Library feature. Users can mark certain items of theirs as publicly lendable. Searching for an item could be location aware, and pick out people near you who have the item available. Contact with that person could occur directly through the site, so personal email addresses are not shared (unless the users choose to do so in their communications).

The family tree app would have almost no profitability and probably an overall very limited audience, but is of the most interest to me. E-Landlord, as you say, would be more of an involved development, requiring more than just legal consultation. It has, I think, a very high potential profitability, but requires the largest investment to build.

The “Where’s My Stuff” concept immediately jumped out at me as a profitable project. I was thinking of adding the functionality of recommendations of additional media products. You sell an exclusive online vendor contract to an Amazon.com or Target.com, or offer non-exclusive deals to multiple online vendors. When I enter that I own Blu-Ray versions of X3, The Incredible Hulk and IronMan, the ad in the margin suggests I may want to purchase the Blu-Ray of Spider-Man 3. All I have to do is Click Here to find it.

Maybe it could also add a wish list. Users add items they’d like to own/borrow to their Wish List. The Wish List searches the ownership lists of friends & family to see if any of them have the resource available for loan.

Should a product recall be offered on any known items, that message could be sent to all known owners. Should a sequel be announced, that message could be blasted.

I just see the most potential in this project of the three. Although, all three sound really good!