No, I got that
No, I got that, but what you didn't quite seem to get is that why stop at just caller ID? Besides the fact that you'd need some kind of hard link to the phone line in the residence or a separate transmitter. The former would kind of defeat the purpose I would think, and the latter is just one more reason why it wouldn't work. We won't get into the physics of antennas.
Anyway, why would companies stop at just caller ID? Why not just go and make it a full fledged cordless phone? And then why not just make it a full fledged cellular phone if you're going to do that much? The amount of difficulty between those is pretty negligible really. It might even be easier to make a cell phone in watch form than any kind of cordless phone.
All of this also completely ignores the fact that people are abandoning landlines in ever greater numbers, so the growth market for any product like this would be to have a cell phone in wristwatch form factor. Who wants to spend millions of dollars developing something that has a shrinking userbase?
My apologies if I incorrectly assumed that you were doing the same basic analysis in your head. I sometimes forget that things that are almost second nature to me, do not necessarily come easy to others.