Set the time on your meter or how long before you need to return to your car or location. Parking Angel will continue to calculate the distance between your car and you, informing you when you need to start to head back to your car. Parking Angel is much smarter then just setting a reminder, if you are around the block or across town, you wont be late to feed the meter! Message someone right from the main screen to let them know where to meet you or let them know where the car is. When its time to head back get turn by turn directions for the best route back to where you started. If you are walking around, keep it in "Walk" mode, however, if you have jumped into a different car, put the app in "Drive" mode and it will automatically calculate the time to turn around accordingly.
Continued use of GPS running in the background can dramatically decrease battery life.