Recently released version 2.3.1.  There was a 2.3.0 release but Google took so long to review it that 2.3.1 was in the queue before 2.3.0 ever made it out.

This release removed a couple of exchanges that are no longer supporting a public rate API.  Also made some improvements to avoid running in the background all the time.

Several changes were driven by a requirement of Google to target newer Android SDKs.  This unfortunately introduced several issues.  The home screen rate widget is not updating on Android 8 (Oreo) or above.  I'll hopefully have a release out soon which fixes this.  Notifications when the rate passes a threshold is working on all Android versions.