The stock firmware of the Pebble Watch only seems to support English and other western languages out of the box. As I sometimes receive messages and notifications in Cyrillic, it was annoying that these were not displayed correctly (i.e. all the unknown characters were replaced by a rectangle)
On the Pebble site itself there is nothing mentioned on how this can be enabled, so it looks like it is not supported out of the box. Fortunately the smart people of PebbleBits have found a way around this and offer modified firmware versions with support for additional character sets and also a small number of other patches. They state clearly that their site is not operated by or affiliated with Pebble in any way but it offers a very interesting Firmware Generator, which offers support for a number of language sets:
- Symbols, Emoji
- Latin-based: English, Croatian, Czech, Danish, Dutch, Estonian, Finnish, French, German, Hungarian, Icelandic, Italian, Latvian, Lithuanian, Norwegian, Polish, Portuguese, Romanian, Slovak, Spanish, Swedish, Turkish
- Cyrillic: Belarusian, Kazakh, Macedonian, Russian, Ukrainian
- Other: Greek, Hebrew, Thai, Vietnamese
For modern firmwares (v2.5+) there seems to be sufficient place to add a number of languages, older firmware versions have some limitations. In addition to adding characters, it is also possible to apply a number of patches to the firmware itself:
- Disable default watchfaces
- Disable default main menu entries
- Display phone number instead of contact name on incoming call
- Additional quick launch options for apps
- Change buttons layout of stock Music app (my favorite as it adds the option to control the volume)
- Translate the interface to a another language
After the selection is made, the custom firmware can be downloaded. This should be done from a smartphone that is connected to the Pebble watch, the site works great on a mobile phone, but also provides a QR code that can be scanned by the phone to download the firmware. The installation is seamlessly done by opening the file with the Pebble app, which guides you through the process.
So far I have noticed that the watch works fine with the patched firmware and supports (in my case) Cyrillic notifications perfectly now.
For reference: here is a link to the configuration I use.