The GPIO port (P6) could be used to power up analogue sensors, like described here where it can provide 3.3V and GND. It can be used for various special applications and it has six multi-function pins. These are not implemented in software and can be used for various custom applications. You can use the port for almost any I2C or SPI sensor, the only thing needed is a driver. Interfacing with other sensors are usually quite an easy task. Here are a few examples of SHT20-variants that we have implemented via the GPIO-port to measure humidity and temperature in the air.
Please discuss your application with AKKR8 AB to assess suitability of this interface to your application.