So there I was thinking about the Samsung Note 3, Nokia Lumia 1020 or Sony Xperia Z1 as my next phone and then Sony launches the QX10 and QX100 lenses.

Sony DSC-QX100 £399
Works with any android or iOS smartphone. Simply mount the smart lens to your phone or hold in your hand or attach to a tripod.
One touch connection with NFC. High-performance 1.0-type Exmor™ CMOS sensor with 20.2 effective megapixels, -F1.8 Carl Zeiss Vario-Sonnar T* lens has a wide aperture to allow more light to enter the camera, for easy, creative effects.
Take complete control – use the functions on your smartphone’s touchscreen to compose and shoot, or use the control ring to manually fine-tune zoom and focus. Get close with 3.6x optical zoom – pull yourself closer to the scene and capture the long-distance shot you’re after. Optical SteadyShot reduces the effect of shaky hands for crisp, blur-free images.
Capture your own HD movies – thanks to the large CMOS sensor, the smart lens will shoot high-quality HD movies (30p) with low noise, even in the dark. Shoot fast, shoot clear – the high-speed BIONZ imaging processor powers rapid shooting for quick and clear results.

Sony DSC-QX10 £179
Same idea as its big brother but a G lens with 10x optical zoom. Optical SteadyShot reduces the effect of shaky hands for crisp, blur-free photos and videos. An 18MP Exmor R™ CMOS sensor ensures crisp, detailed results in every frame.
No noise, just smooth images – back-illumination technology inside the sensor collects light more efficiently to ensure minimal levels of noise. Capture your own HD movies – thanks to the CMOS sensor, the smart lens will shoot high-quality HD movies (30p) with low noise, even in the dark. Shoot fast, shoot clear – the high-speed BIONZ imaging processor powers rapid shooting for quick and clear results.

So with either one of these lenses I could attach these to my Nexus 4 and have a super HQ camera.
Also the lens has its own battery and memory card slot, so not drawing on my phones battery. The lenses can be used without the phone to.
So is this a great idea or a nutty one? Well it is in the top 3 at Amazon!