Only school I know of that uses ProctorU is University of the People but they do not have a regional US accreditation, so likely won't be valid for applying to OMSCS afterwards. Every town though will have some kind of invigilating/proctoring service you can rent. All the local colleges, libraries and universities in my city do this for a fee.
I don't need to apply to OMSCS...I was just saying it offers 100% online, including proctored tests. No need to go to get a proctor or go to a testing center, which is inconvenient for me. They used to use ProctorU, but switched to ProctorTrack. I don't know what they use right now.
Edit: Just checked and UOP doesn't seem to offer a math degree at all, so that doesn't help me.
