I am a complete newbie when it comes to carputers.....just found out about them the other day

But I am no noob to computers or technology, so I already have most of my hardware picked out.
I have been doing some reading on the subject and have looked at solutions like centrafuse, and roadrunner but Im just not sure what all is really out there and was hoping for some suggestions on what to look at.
Must haves:
Play cd/DVD disc
Play MP3s from hdd
Play videos from HDD
Navigation
Like to haves:
OBD-II interfacing
Control with blackberry or iPhone
play music Wirelessly from ipod touch (will have in-car wifi)
Interface with phone, make/receive calls.
Now im not really sure what I can do with the OBD-II stuff, but I heard it can do reporting on like speeds, rpms, etc.
Also would i be able to, maybe with other software be able to program the ECU with this carputer?
I know this is a lot of stuff, but if I could get pointed in the right direction I would really appreciate it.
Thanks
Stephen