Blighty

This plugin monitors installed WordPress plugins on your installation. It notifies the admin (or other email) when updates are available. Plugins can be excluded from monitoring.

Blighty Pluginator

This plugin monitors installed WordPress plugins on your installation for updates and notifies via email when they are available.

WordPress.org

Dion Hulse

Andrew Nacin

Most sites are able to apply updates in the background. Background Update Tester checks your site for compatibility and explains any problems.
After activating this plugin, visit the Dashboard → Update Tester screen. (If you are using multisite, visit Updates → Update Tester in the network admin.)
This is an initial release.

Background Update Tester

Most sites are able to apply updates in the background. Background Update Tester checks your site for compatibility and explains any problems.

Blighty Pluginator vs Background Update Tester