Nginx, Is client using SPDY?

Is there a way to know the client can use or is using SPDY and then route that SPDY client specific data, Ie http<- site1, https<- site2, SPDY<-site3 (all have to use same domain and ip address)?

I have tried using the alternate protocol header to suggest to an incoming client that my server is SPDY capable and they should switch to port 81 to use SPDY, but all browsers only seem to follow this suggestion if the suggested port is 443 (against (under Deployment) what Draft 2 of the SPDY doc suggests). using 443 would interfere with my HTTPS data. Any suggestions on this issue?

Thanks in advance.