Passive NFC powered devices already exist, for example.
Radio transmissions obey the inverse square law, so the amount of energy you receive rapidly decreases as distance increases. That's why RFID devices only work at extremely short range, typically less than 2cm. If you wanted to keep your phone in your pocket it would either need to send out extremely powerful transmissions or the watch would need an extremely large antenna to receive enough energy to do anything useful.
Can't change the laws of physics, captain.
A pacemaker can run 5-10 years on a battery. A wristwatch that mechanically moves hands and dials runs for years on a single battery.
You make a very common mistake which is to vastly underestimate the amount of energy required to do those things. Pacemakers and watches only need very, very small amounts of energy to operate, several orders of magnitude lower than is required for Bluetooth or the processing required to generate graphics for a low power display.
The only way smart watches will ever last for years on a charge is if we develop some currently unimaginably efficient energy storage device. It would have to be based on some pretty exotic physics because nothing we can image as being practical for now could do it. Either that or we discover a way to send subspace messages instead of using radios and it happens to require almost zero energy.
A few weeks, a month maybe, but not years.