I want an extended-life battery that can be used simultaneously with a slider-type Innocase. I've gotten too spoiled by my Hero's extended-life battery to ever go back to a wimpy stock battery that needs aggressive power management to last half the day, and the Epic4G feels totally fragile compared to the Hero (which doesn't exactly exude an aura of rugged durability, either).
Going a step further, a longer case with 8-way gamepad at one end (extending the phone's length) and hardkeys for home/back/menu/search/send/end sitting on top of the capacitive ones at the other end would be awesome. There's even a perfect way to get the signal from the buttons/gamepad into the phone... the 1/8" mic jack. Just treat the mic jack like a hardwired ~14.4kbit half-duplex serial port with return-to-zero signaling and ~1v highs, and bit-bang the sampling. Assuming, of course, that the Galaxy S phones don't actually HAVE a CMOS-level serial port ALREADY sharing pins with the headphone jack as alternate functions (I'm pretty sure at least one Android phone does that already... the G1, maybe?).
Give it a small lithium cell of its own built into the case to power it, and leech power from the micro-usb connector when it's connected to a power supply to charge it (possibly using one of the other pins on the headphone jack to signal to the interface that the phone is fully-charged and that it's OK to begin drawing power from the usb to charge the case's battery). In a pinch, Seidio could even totally hijack the headphone jack and use it as a power source... have the phone output a 22KHz sine wave at maximum power, and feed it to a high-efficiency switching power supply to convert it from ~.7 volts AC to 2.7-3.3vDC.
Sigh. I really, really need to get my hands on a 3D printer so I can try making stuff like this myself someday ;-)
