Unless you plan on having a site with just a small number of users it will be a waste of time to create an Etano login bridge for picpin.
The main problem with most PHP and/or Ajax based chat or messenger scripts is they tend to be rather resource intense, even if you have a dedicated server you will be pushing the envelope with 100 simultaneous users chatting at once, a shared hosting plan will handle far less, in many cases anymore than 25 or 30 will cause it to crash.
The reality is if you want a decent chat or instant messenger for one-to-one chats it's going to cost you. About the only one-to-one chat system that's really worth considering is http://www.cometchat.com/
which is very similar to Facebook's footer chat, which is what most dating and SN sites are going with these days. They even have an integration mod for Etano http://www.cometchat.com/etano-chat
. You can start out with your own hosted solution of comet chat and as your site grows and you can expand on it using their push services that can handle hundreds and even thousands of simultaneous users.