I think this is a standard feature of most modern touchscreen smartphones and not some "design brilliance" relegated to only Apple devices.
I currently have to carry two phones, one is an Android device and the other is a Windows Phone 7 device, they both implement the proximity sensor and it works the same way as the iphone.
IIRC correctly HTC (back in the days of Windows Mobile 5) already employed this feature in their "slate" phones before the original iPhone was released. They then improved it by adding some rather unique features, like being able to flip the phone over (i.e. laying screen side up on a table) to silence/reject an incoming call.
I didn't use the HTC phone that you mention, but it would be interesting to know if the feature was implemented as well as it is in the iPhone. This feature has literally never failed for me in 2 years of using my iPhone (it sometimes gets false positives when the phone is in my hand, but it's not too bothersome).
I currently have to carry two phones, one is an Android device and the other is a Windows Phone 7 device, they both implement the proximity sensor and it works the same way as the iphone.
IIRC correctly HTC (back in the days of Windows Mobile 5) already employed this feature in their "slate" phones before the original iPhone was released. They then improved it by adding some rather unique features, like being able to flip the phone over (i.e. laying screen side up on a table) to silence/reject an incoming call.