Check out the iBike Dash (I am a bit biased to it), but it really does have all the features you guys have stated you are looking for.
It comes in a solid waterproof case.
Rechargeable, replaceable battery (it'll drain the external battery before your iPhone)
Heart rate, cadence, hill slope, even power available (It's ANT+ Sport compatible)
You can just push a button and it'll email you a ride file, no more manual downloading. Last I talked to the owner they are starting to work on one-touch integration with the Strava website.
They do have a few different levels of the product available, everything from just a case to a full blown power measuring device.