It is possible to get data from Android about how much it has used it core in the processor.
For those who are technically minded, the information can be found in the /proc/stat file.
I wrote a tool which grabs the per core usage information from Android while an app is running.
To increase the efficiency, and lessen the performance hit of the monitoring, the data is only collect while the test app is active.
The analysis of the collected data is done “off-line.”