For the first point, there resources out there, but I personally don't think there are many that are that easy to use and work with other social sites. This is actually an interest of mine and is the first side project that I have started working on. I hope to have something out there in the not-to-distant future and I hope to get feedback from people like you who are also looking for such an app.
Great. I would use it. Build it and I will come :)
Do you need help?
Possibly. I'm a Python guy doing this is Pylons so if you have experience with that, I would take some help. Also, if you have any experience with interfaces, that's my weakness.
Anyone who's interested in working on #1, has some time, and can work with Rails3/Ruby, send me a note. Contact info in my profile.