> Having ff on an ipad and phone is really not having a “common point of failure”
The “common point of failure” is GPS, which does have regular local/regional outages. Your instruments may be able to use VOR/DMEs, and hopefully you're able to use the VOR MON:
MON just means that there are a certain number of VORs that aren't going to be decommissioned. it's not a different kind of VOR. and they're decommissioning all of these VORs precisely because GPS is so reliable.