I have published an update for CalJ on Androi. Version 2.20 features a new tool that is not yet available in the iPhone edition: a compass to Jerusalem for the direction of the Tefila.
The Sages have fixed that the prayer of Amida must be said when facing towards Jerusalem. The synagogues are generally oriented more or less towards the Kodesh haKodashim, but an individual who prays at home or out in a journey needs to know the direction to turn to.
Heading to the Kotel varies with the location. When opening the screen, and if the GPS sensor is off, the CalJ app considers that your current location is the town that is configured for the Times screen. GPS is not mandatory for the compass to work.
If GPS is on, the heading adjusts automatically.
Instructions of use: turnem around to make the red arrow point straight in front of you.
A word on accuracy
Android devices are equipped with an electronic sensor to guess the direction of the magnetic North pole. The signal is extremely disturbed by the presence of metallic objects or electric devices.
Make sure to keep the phone horizontal away from any magnetic disturbance.
Besides, the geographic North differs from magnetic North reference by a few degrees, depending on time and location. But this still complies with Halacha, which rules only on an approximating direction for the Tefila. The orientation is only symbolic and does not require absolute accuracy — unlike the Zmanim rules (times).
Please feel free to comment and report any feedback.