It should be possible through custom scripting and crontabs. Your custom script should run the speedtest package and the current timestamp of the device. Then you will create another script to send the results with a given schedule.
Helpful commands: echo “y” | speedtest > test.txt - This command will run the speedtest package and save it in a file (test.txt). date - Shows current timestamp of device. crontab -e - This is where you will schedule when the custom script will run.