UK-based Tech 21 have devised a real-life, mailable, flubber-esque gel that becomes rigid on impact. This substance dubbed "d30" is used to safeguard an iPhone or iPod Touch from owners with buttery fingers.
According to the product page, d30 cases can offer up to "150% more protection than other cases". Of course, that protection doesn't extend to the screen, which is probably your number one concern. [Tech 21 and Recombu via CrunchGear]