bower-outdated

This command will check the bower registry to see if any (or, specific) installed packages are currently outdated

Install

npm install -g bower-outdated

cd <path_to_you_project> && bower-outdated

Very similar to npm outdated command

package name is red if current version (in bower_component) doesn't match the bower.conf requested range version
latest available version is displayed, it's up to you to decide to update or not (always check the release note first!)