We are running a membership site. However, we have a problem with users that subscribe to our content that are sharing there login information with other people, circumventing the need for those users to also need a subscription. Any ideas for plugins that already do this? Or suggestions of how to go about logging people out that login from 2 locations? I assume some use of IP addresses per login or something...?
We had a similar problem where we needed to give access to partners and "membership" or "subscription" plugins seemed to offer what we needed. The problem we had was that the plugins we found were all for-pay, not free or freemium.
Understanding this, the MagicMembers and aMember Pro plugins both had functions that could prevent access sharing. I'm sure there were others, but the spreadsheet I used to compare the different products (and a quick check of each site) turned up these two as explicitly doing what you need.
The costs of these can range a great deal. I'd suggest searching with terms like "wordpress subscription access sharing" and seeing what turns up. "Access sharing" is what most of the plugin developers called the situation you are describing...so that might also help.
Check out this plugin
This plugin already does this your requirement.