WP-Requirements is nice little library that I extracted out of a few plugins that I am writing. It allows a very easy way to manage both checking for system requirements and displaying them to users.
It uses a neat technique by Square Penguin. The idea is to use the double request that WordPress makes while activating plugins to display custom error messages to the user.
This allows you to change a cryptic plugin activation message like this,
into a more relevant message like this.
The plugin contains a
FauxPlugin that goes about the WordPress plugin
activation lifecycle internally. The advantage with this approach is
that your real plugin doesn’t need to change at all.
Only if the requirements are satisfied does your real plugin kick in. The
FauxPlugin is like a failsafe to ensure system requirements are met.
If you build specific types of plugins you can easily build a custom
MinRequirements class that can be reused across all your plugins.
More information is available on the GitHub project for WP-Requirements.