The NLnet Foundation has been sponsoring Collabora to do some smart card work, and this is part of that. This work is part of the GCR library, and is merged into gnome-keyring master.
Here's a certificate viewer showing a certificate:
Details can then be expanded:
And here's what a key looks like.
When the file is locked (like a PKCS#12 file) it can be unlocked like this video shows. It also shows the appalling state of affairs with hundreds of certificate authoritities, dubious and otherwise.
In the next release, we'll have an "Import" button in the bottom right corner, so that the certificates and keys being viewed can be imported and used into common locations. Hopefully we'll also get able to view PGP keys in files (before importing them).
The widgets you see displaying the certificates can be used by any application from the GCR library.