Net Nanny can be purchased for one or more computers at http://www.netnanny.com/products

Protect 1 computer for - $39.99 a year - additional seats $19.99 each
Protect 3 computers for - $59.98 a year - additional seats $19.99 each

Important: Net Nanny needs to be installed on each computer you are trying to protect.

Net Nanny is also available for Android mobile devices for $19.99 a year per device.