Not sure what the answer to this one is but it made me think.
There is no in flight aural warning if the brake is set
The a320 series parking brake like all the airbus family applies only 1/2 max pressure ( regardless what the guage reads ) and thats one reason engineers need their feet on the pedals for full power engine runs.
As to what would happen on landing if it were set my guess would be a very rapid stop