We already collect that information about relaying IPs (although you can never really be sure who is the originating IP). We have custom nodes that specifically listen for that information. However, we decided this wasn't useful enough to be included in the versioned API.

Although, we are about to release labs.helloblock API, which will include a bunch of experimental features, including information about IP addresses.

Out of curiosity, what do you plan to use information about IP addresses for?