I'd just heard about the $1 USD “bumper” case for the iPhone 4, but how about a dock? — I initially refused to pay $29 USD for a dock accessory that'd be compatible with the iPhone 4. On a whim, though, I tried it with the dock from the original iPhone…
… And, it worked! 😲
… I couldn't believe it! Finally, some return on my investment from the original iPhone, which I infamously hated. 😅
UPDATE: John Adams tried dremeling out his iPhone 3GS dock, without luck. 😓 It didn't work… but for whatever reason, this one does? — Something about resistor codes to identify the accessory or device… very sneaky! But, not as sneaky as this. 😉