The ideal way of getting this isn't to grab stuff just from Twitter. It's to have a way of including RSS feeds (with options) as sidebar modules.

I'd like to have my most recent Tweets and my most recent posts on other blogs displaying (in seperate modules)—if we can figure out a way of having an S2 layer that parses feeds well that'd be really cool and would provide you with your solution as well as being more flexible.

But yeah, no chance of getting a flash or JS embed to work here, and I think that's a policy that should stay.