A few US states have developed their own applications for ID cards and driver's licenses that are digital. California is one of those states, but Google Wallet for Android will soon support ID cards as well.
The California DMV is testing compatibility for Android users in addition to Apple Wallet for iPhone owners.
Users won't need to download the CA DMV Wallet app in order to do this. You can actually keep both. Instead, Google Wallet handles every step of the setup process:
Google Wallet's California ID feature is presently under beta testing with DMV personnel from the state; it is not yet available to the general public. Since then, pages describing the pilot have been removed.
Considering that Google Wallet only last week introduced support for iPhones, Ohio may be the next state to receive the service. As of right now, Arizona, Colorado, Georgia, and Maryland are on the list.