Anyone know of a service that supplies this that isn't youtube? I know youtube has this functionality baked in, but in my experience, many people ask for custom video players, which are very possible with videoJS, but getting the right video dependant on connection is key.

I know of no service that offers this atm. Specifically where it will serve up a specific url you can stream from independent of player. In the past I have used Vimeo to serve up the files, but hosted them in a custom player. It's possible to write your own script too that will do crude detection of a network speed, but wondering if anyone has any other answers to this.