NordicTrack has launched the iSelect Adjustable Dumbbells, which you can control with voice commands via Alexa. The weights can adapt to loads from 5 to 50 lbs (~2.3 to 22.7 kg).
https://www.notebookcheck.net/New-NordicTrack-iSelect-Adjustable-Dumbbells-can-be-controlled-using-Amazon-s-Alexa.591934.0.html