Open Source (some free and some not) MDM

https://github.com/micromdm/micromdm
https://github.com/multunus/onemdm-server
https://github.com/multunus/onemdm-client/blob/master/README.md

http://wso2.com/products/iot-server/

https://developer.android.com/reference/android/app/admin/DevicePolicyManager.html
https://github.com/oddmouse/cordova-plugin-locktask

https://www.miradore.com/miradore-online-for-mobile-device-management/
https://www.codeproof.com/
https://meraki.cisco.com/products/systems-manager
https://www.apptec360.com/solutions/mobile-device-management/
https://www.hexnode.com/mobile-device-management/
https://dm.comodo.com/