I was just browsing the eshop and noticed it. Does anyone know what it actually does? The very minimal amount of info on the shop doesn't help at all, other than telling me it's an update for StreetPass.

You can create a streetpass profile card for your SMTIV character. It shows what level you are, what stats you have. Stuff like that. You can also offer up a demon to be put into the card and can be transferred to other people. The downside is that demon isn't usable when in the card. It's just streetpass shit for SMTIV.

That's not actually what I was asking about. There's an actual update on the eshop that you have to download.

After a little digging it appears it just allows you to access the Streetpass bonuses for Streetpassing someone with Etrian Odyssey 4 or Soul Hackers.

I wasn't to the point where I was able to turn on Streetpass when I downloaded the patch then. In fact, after downloading that update and playing a bit I unlocked Streetpassing so I always just assumed that it gave the streetpass functionality to the game. My bad.

I wish I could just get those bonuses if I owned the games, since these titles aren't amazingly popular.