Imagine it.  No pulling out your wallet from your back pocket.  All you would need to do is look at the watch, select wallet app, scan tap send address, select amount and send.  You could also save that address to use again if you are a regular customer.  I could see restaurants that have a queue like Chipotle accepting BTC because it would speed up the payment process.  You could pay while you stand in line, without having to deal with a cashier.

On another note.  Maybe Apple should make the iWatch free or even pay some bitcoin to people for wearing it.  Does anyone notice the enormous hear rate monitor on the back?  This heart rate monitor uses both green and infrared LEDs to measure pulse.  What other function could a infrared LED with a photodiode receiver be useful for.  Hmmm. Infrared Spectroscopy is a field that makes possible analyzing specific atoms, molecules, and compounds in solution.  Perhaps the infrared spectrometer on the iWatch could be useful for collecting in situ blood chemistry data?  

Whether or not Apple intends to do this or not has not been disclosed, but it is still peculiar that the watch would come with this equipment if its only function was an over-priced inferior (compared with EKG measuring) heart rate monitor.  If I was an engineer at Apple working on this hardware, I would want the hardware to measure everything imaginary possible.  Heart rate monitoring is caveman technology, I would want it to measure every compound in the bloodstream.

(While we don’t anticipate a loss of cabin pressure, in the unlikely event that one occurs, a tin foil hat will drop from the overhead. Pull the hat down to start the flow of manic paranoia, and place it over your eyes and ears.)

All joking aside, the potential of this technology is huge.

I'm going to use bad logic here but I will continue on anyways assuming hypothetically that the iWatch could analyze blood chemistry (Perhaps iteration number 3 or 4 will, and Apple only included it on version 1 to get the customer familiar and comfortable with it).  What customer would pay for something like this?  This would be equivalent to paying for an instrument that could monitor the 'health' of your car, and all imaginable car related data being included; speed, parking location, signaling, running red lights, tailgating etc etc.  On the one hand it would be nice to monitor and record data from the engine, oil, belts, frame, wheel alignment, electrical problems...  but the devise would force you to disclose all details of your driving habits.  If getting a ticket from a speed camera a week after it snaps a pic of you makes you fly off the handle, imagine receiving a tab for all the petty traffic violations you committed on your morning drive to work upon arriving.  Also, perhaps your mechanic and the sheriff would be interested in this data.  Relating it back to the watch; perhaps similar parties might be interested(insurance company, and employer, and bank, and...)



TL;DR - Bitcoin would be an awesome app on a smart watch (duh). Apple put a infrared spectrometer on the iWatch to analyze and monitor your blood chemistry. (pure speculation)