Ring and OnTech, for example, charge $65 to $215 per additional device, so you get a discount but you’ll still have to pay for each cam you install. Other vendors may charge the same installation fee per camera until a certain number is reached. For example, two cams may cost $200...
Charging the Oura Ring from a fully depleted battery takes about 80-120 minutes using the included USB charging dock. Actual time varies based on remaining charge level. Quick charges can provide sufficient power for the day.