PLC IO redundancy is a common property of safety PLCs in which each IO has a redondant signal processing.
For example, several SIL3 PLCs use a Triple Modular Redundant (TMR) architecture with a 2oo3 voting on each IO. You can also find Double archirtecture with 1oo2D voting or QMR architecture with 2oo4 voting.
You will find examples of such products if you look at manufacturers like Triconex, ICS triplex and HIMA.