Pressure is an impromptu phone-into-balloon effect.
It can done using basically any balloons (ie: Party Balloons or Water Balloons (in my opinion water balloons can be a little too weak to perform this effect)
It requires not prep-time it is completely examinble in the end and you can achieve this effect with any object you can get your hands on (ie: Phones, iPods, Canned Beverages or food, toys or cards)
Hopes this can answet any question you may posted or have.