When you mention otterbox, please keep in mind there are several, although most popular are the defender and commuter. I have a commuter and its great. Not on the bionic, but still. The unit is two pieces, a silcone inner shell and a harder plastic cover. It's not bulky at all. Included a clear screen protector which went on easy and you can't tell I have one on.
The defender is the bullied one and basically protects against everything shot of dropping it in water. Should be enough for a casual spill. The screen protector is part of the unit, not an applique like the commuter is. I've seen it on other phones and it is much more bulkier
Sent from someplace, and with something that you need not worry about.