Content Filtering 1 to 1 Peer Review

Currently, we have an EU using Untangle for their content filtering. What they're telling me is they have accounts created for their employees to log into so they can review the content filter, and basically audit everything that only 1 other person is doing and vice versa. This way they have people auditing each other and keeping them in check, rather than 1 person keeping track of everyone. My questions is, does anyone know of a hardware Security Appliance with content filtering that would offer the same capabilities,  or if one even exists?