I just downloaded 13.5. So, I figured I would check out the tracing apps. Is there any kind of reference as to which to pick? I've seen them for Singapore, New Zealand, and Utah. On one, I can't remember which, it seemed to indicate that you had to have the same app as someone you were near for your phones to communicate. Deciding whether or not to use this feature seems is the easy part. Picking an app is my sticking point.