These two types of RAID are made for different purposes.
RAID 0 is used to speed performance, while RAID 1 is used for data redundancy. From your brief description, it sounds to me that you will be wanting redundancy (RAID 1)
Essentially, RAID 1 writes the same data to both drives at the same time. Therefore, if one of your drives fails, you can recover the entire contents from the other drive.
RAID 0 on the other hand 'stripes' data across two drives. Essentially, it splits the data you want to write in half, and writes half of it to one drive, and half to the other. In principle you can get twice the read/write speed with this method, although of course in practise the gain is somewhat less. Note that RAID 0 offers no redundancy; if one of the drives fail you have lost at least half your data (and reconstructing the rest of it may be difficult).
Do your drives currently write fast enough to record all of the data from your cameras realtime? If so, go with RAID 1 for redundancy. If not, go with RAID 0 for the performance boost.
I doubt you are maxing out the write speed of a single WD green ( 100MB/s) with three surveillance cameras, unless they are something like full HD with high FPS.
See this website for more details on RAID:http://www.thegeekstuff.com/2010/08/raid-levels-tutorial/
Edit: Sorry, didn't see the latest replies.
Particularly if it is just storing motion, then there is absolutely no way you are hitting a performance bottleneck. Do RAID 1.
And like the other poster said, the viewing from a cellphone will be completely separate, don't worry about it.
Just one final note: RAID 1 IS NOT A REPLACEMENT FOR PROPER OFF-SITE BACKUPS! This will protect you if a drive fails, but if there is a fire or something that destroys your computer, you are still out of luck. If it is important, do an offsite backup regularly.