Gallery opens itself on ZenPad10 while the screen is off
After fiddling with some options earlier, I actually came accross the answer on accident. This is from a feature called ZenMotion, something ASUS started implementing in their Zen phones and tablets, I believe.



Note that not only this answered my question, it also showed me that there were 5 other shortcuts available, with each letter being able to be linked to a different app if I chose so.