I’m trying to cut down the amount of time I spend on my phone. I thought some sort of wearable might help. I’ve realised there are three reasons I can’t just leave my phone in a drawer when I am at home:
What are your opinions on the best/easiest/cheapest way to do this?
The cheapest way is to set your phone notifications such that you are notified of what you need to be notified, and buy a cheap analogue watch.
This is from someone who is desperately trying to resist buying an Apple Watch for pretty much the same reasons you give. 
The only downside to this is I’m not sure I would hear the notifications if my phone was in another room in the house, and I’m trying to avoid carrying it from room to room to break the habit of using it so much. I’m slightly hard of hearing at the best of times. I don’t even know what the price range of wearables are 
I know what you mean. I bought my cheap watch because I’d use my phone to see what time it was, 30 minutes later I’d put my phone down and still not know the time!
The real solution is to get rid of as many notifications as possible. I asked myself if I really needed to know if someone just sent me a message, or could it wait a while? The answer was that I could live quite happily not knowing.
This thread is old, but maybe helpful?
So I bought a pebble from facebook marketplace for £5 and so far, it works! 
Tomorrow will be the real test. I plan to leave my phone in a drawer until I leave the house 