Android Application that detects SMS and sends web call

This android application needs to have a first page which will ask for a key, then after the key is entered it will change to a page that displays the option to change their key (simply remove the stored key and send them back to the front page) and a checkbox to send/not send phone numbers. In the background, the application will send two different REST calls. The first call will be to an endpoint which will verify that the key can be used. The endpoint will simply receive a key and a randomly generated string that must be stored on the device (a unique ID). If the endpoint returns a success message, the system will proceed to the next page. If it returns a failed message, a 'popup' notification will be displayed displaying an error message to the user and asking them to enter a new key. The second call will be to an endpoint every time a new text comes in or when the text is read. When a new text comes in, it will check the stored setting of whether the user has opted to send or not send phone numbers. If the user decided to send phone numbers, it will send the unique id, the key, phone number and a +1. If the user decided not to send phone numbers, it will simply send the unique id, the key, and +1. When a text is no longer marked as unread, it will send the unique id, the key, the phone number (if the user has opted to do so), -(the number of texts just marked as read). For example, if 12 texts are read, it will send -12. Since texts can be read in bulk, it is important to group them as much as possible. If this proves too difficult, sending multiple -1s is acceptable. The interface will be very simple. When the app is first opened, the splash page will be shown which will consist of a soft, subtle gradient and some thin white text with black outlines. While the app is opened and visible, the app will have a gradient background which gently changes colors (the text must be still visible, if this proves difficult a non-changing gradient background will be acceptable). The color changing should not be running in the background if the app is not on the foreground, but the portion of the code that monitors the SMS statuses should always be running once the app is opened (unless it is killed). Emphasis on battery life and simplicity are a must. Thank you.