I would like to see a feature for items that collect numbers to have a "running total" preprocessing option.

As an example, the net.if.in and net.if.out can collect in and out byte counts for a particular interface. These interface counters (in linux) reset to zero when the operating system restarts.

A preprocessing step (or even just a on/off button) that would collect the value from the host, calculate the difference between that value and the previously collected value, then add this newly calculated value to the previously stored value.

This feature would facilitate collection of interface in/out byte counts that persistent between host reboots.

This can be partially accomplished through a calculated item, but since calculated items cannot be linked to master items (throwing execution times out of wack), I figured that adding some logic into the original item would be the simplest/most elegant solution.