8. A portable electronic device for presenting a recommendation message, comprising: a display; a motion sensor; one or more processors; and memory storing one or more programs for execution by the one or more processors, the one or more programs including instructions for: detecting a trigger event based on a user input in an application running on the portable electronic device, the trigger event initiating a predefined time window for receipt of a non-tactile user input; in response to detecting the trigger event, receiving sensor data captured by the motion sensor resulting from a non-tactile user input, wherein the sensor data is captured within the predefined time window; determining whether values of the sensor data captured by the motion sensor satisfy a predefined movement pattern of the portable electronic device; in response to determining that the values of the sensor data satisfy the predefined movement pattern of the portable electronic device, generating one or more character strings based, at least in part, on the values of the sensor data, each character string of the one or more character strings including multiple characters; generating a recommendation message that includes the one or more character strings; and displaying the recommendation message on the display.
13. The device of claim 8 , wherein generating the one or more character strings based on the values of the sensor data comprises: generating the one or more character strings in a first specified value range upon determining that the values of the sensor data satisfy a criterion; and generating the one or more character strings in a second specified value range upon determining that the values of the sensor data do not satisfy the criterion, wherein the second specified value range is less than the first specified value range.