Researchers at the University of Michigan are taking a cue from Apple to create a pressure sensitive phone. Their software, ForcePhone, relies on a device's built-in microphone and speaker. With this software installed, the phone's speaker constantly emits a sound at a frequency of 18 kHz. This is inaudible to human ears, but not dogs'. Poor dogs. Whenever a user squeezes the phone or presses down on it, the tone of that sounds changes and the microphone recognizes it. It then translates that change into a command.
The researchers believe their work could allow cheaper phones to be pressure-sensitive because they wouldn't require extra sensors. Maybe someday soon we'll be giving our phones hand hugs.