Developer's note:

As promised, here’s the unfinished version of SMS Plus with Ad-hoc play. I’m posting it here with the hope that someone will be interested enough in continuing/finishing the project. Please note that the program is pre-alpha, and unsupported – it will allow you to start and play ad-hoc games, but the two sides may eventually get out of sync and go off on their own. Additionally, once you leave a game to return to the menu, you may not be able to resume the game successfully.

To get started, load a new game, and return to the main menu. To host a game, open the Netplay tab, and select Host game. To join a game, open the Netplay tab, and select Join game. A list of hosts will appear on the right-hand side of the screen – select one and press X. The host will send the client the ROM (client doesn’t need to have it), and the two sides can start playing. Host is always P1, client is P2.

Again, please note that this program is incomplete. I offer no support for it; I’m only posting it here with the hope that someone will be interested enough to finish it. Full source code is available from my PSP SVN repository.