Can the Sling take over and develop a app for the PSP?
Sony has discontinued their LocationFree devices and LocationFree software a long time ago.
Besides, their PSP LocationFree software has a bug witch prevents it from controlling a video source from the Internet (I am guessing due to lag, because it works fine on LAN).
50 million PSP users want streaming video.
Whilst it is not LocationFree you can achieve video streaming to a PSP over the internet with a PS3 + PlayTV.
Have a look here http://www.playtv.me/watch-tv-on-psp.htm and you can see what I mean.
This may be an expensive solution to your problem but who doesn't want a PS3 and if we all buy a PS3 we can then ask slingmedia for a PS3 app too.