There was a port to the DO003 smartwatch (nRF51 16k) but realistically it wasn't usable for much due to the low amount of memory.
There are some nRF52 smartwatches out there which Espruino could run on - some people have even reverse engineered some of them: http://www.rogerclark.net/new-nrf52832-based-smart-watch-available/
However it'll require quite a bit of work, and I don't believe the firmware update keys are available for the watches - which means that you'll have to take every watch you want to use apart and flash the firmware with an nRF52DK by hand.
For quite a while I've wanted to get enough people interested that I could do that work myself and place a large order for watches with custom firmwares pre-programmed, but I'd have to get well over 1000 orders before they'd be interested in talking to me.
This thread is first google hit for "espruino fitness tracker" so I am just letting know here for anyone searching for it that there is now a nRF52832 based fitness tracker that works fine with Espruino. It is the DS-D6 mentioned in the espruino on you watch thread.
The procedure of update from original firmware to Espruino needs only using 3.3V TTL serial port connected to usb pins of DS-D6 and is relatively easy.
More info here https://github.com/fanoush/ds-d6/
It is currently easy to buy it e.g. from Gearbest for $9.99, the manufacturer is Desay as also mentioned in FCC documents https://fccid.io/2AEMN-D6
However as it is sold for quite some time already (at least Gearbest has first user reviews for it starting Nov 2017) it may become obsolete any time soon.
I got few of them for personal use so I will maintain current Espruino builds for it for as long as practical.
Nice - thanks!
Just to add, we now have official Espruino smart watches:
Our current fitness tracker uses nRF51 and is written in C.
It has an accelerometer, Flash, EEPROM etc. etc.
Help will be greatly appreciated!