Using NrfConnect on iPhone reveals the Bangle, connected to it, and it shows the advertised services. Writing to 78290002..... works OK.
To make sure I disconnected the Bangle from NrfConnect, and reconnected. The data I had written was displayed as I sent it. I GUESS this means that the data is written to the Bangle succesfully.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I tried the script on my Bangle:
78290002.....
works OK.Maybe this helps?