Simplistic addon to show a some details of your crit chance vs crit cap. You can either show just a simple tiny text area, or a small graph for the past X number of seconds of time showing crit/cap over time.
Crit cap worked out as: 100 - (dodge - expertise) - glancing - missrate (see: http://elitistjerks.com/f31/t76785-crit_depression_combat_table/)
Options for chat warnings when you exceed the cap, showing by how much. Summary at end of fight showing % of time capped and how many seconds that totals.