Valve are upping their security with the beta roll out for their new Steam Guard Mobile Authenticator for iOS and Andriod devices.
Currently steam only supports Two-Factor security checks through e-mail with Steam Guard, but now valve plans to offer a more convenient and easy authentication through the use of your mobile. This provides the user with two-factor login to steam through the use of your iOS or Android steam phone app.
At the moment the app is only available for the recently updated Android app but plans to move it to iOS are soon to roll out for testing when it updates.
For anybody who wants to take part in the new Steam beta can do so by joining the Steam Community Group. Valve are planning to choose a small number of people for the beta users from the group for preliminary testing and then if all goes well they plan to open up the beta for everyone.