Thanks, Dirk.

To all Jolla users interested in electronics, DIY devices, etc : enjoy while the BreadboardTOH kit is available. BreaboardTOH allows to connect Jolla smartphone with hundreds of different I2C devices/components, which are usually marketed to Arduino, Raspberry Pi, etc :
- screens (OLED, etc);
- EEPROM;
- analog to digital converter (ADC), from 8 to 24 bits;
- digital to analog converter (DAC), from 8 to 24 bits;
- IO extender (to 8 or 16 bits);
- many sensors (directly with I2C or using ADC) :
* intensity of visible, IR and UV light;
* magnetometers, accelerometers, barometric pressure, etc, with more accuracy and less noise than the builtin in smartphone;
* IR range finder up to some meters;
* ultrasound range finder up to some meters;
* laser range finder up to 40 meters.
Almost all of these components costs less or about US$10, needs only some jumpers/wires to connect, only some lines of programming (shell, Python, Qt Quick, etc) in Sailfish OS, or even without programming if you use I2C Tool.

No other smartphone I know has I2C interface available. Jolla smartphone may be the unique one.