There are quite a few, mostly US based, but they are pretty expensive. I lloked at Imerge and ESP-AV (UK company) but there's also Kalidescope. These are all media servers from what I remember but you're talking £10K price range !!
I ended up buying a NAS box (Synology DS1010) with 10TB of disk space, ripped the disks, and then you can play via something like a WD TV Live DMA box. I also took the opportunity to rip all my CD's at the same time.
It all depends on your budget and how many DVD's you have I guess