dbstopif(condition)

dbstopif is a much faster replacement for the built in conditional breakpoint

When working with long loops of processing one may need to set a breakpoint to stop on a particular condition. While Matlab's built in conditional breakpoints achieve this, they exact a heavy performance penalty (even when disabled!), and are not generally maintained between sessions. dbstopif is inserted as a single line of code which which, if the condition is true, sets a regular breakpoint on the following line, resulting in an immediate dbstop.
A comparison of the time to execute a loop with many iterations:

Matlab conditional breakpoint enabled: Elapsed time is 34.412000 seconds.
dbstopif: Elapsed time is 0.004994 seconds.

Disabled:
Matlab conditional breakpoint disabled: Elapsed time is 51.132263 seconds.
dbstopif: Elapsed time is 0.004941 seconds.

Matlab conditional breakpoint removed: Elapsed time is 0.004422 seconds.
dbstopif: Elapsed time is 0.004628 seconds.