Well I am not sure about slideshows or if anyone has written any. However I will respond generally here. For instance if your photopost server allows EXTERNAL MYSQL CONNECTIONS which it would have to allow for this to work you could define a special mysql user to access your database. If your remote site does php you can show an external photo block on that site like so
Reeftalk Photo Block
There are many external photo blocks in the MOD CORNER you can see if any suit your specific needs.