PiJuice HAT - Portable power platform - Pi Supply

This is what Pi Supply says about the PiJuice HAT:

As one of the smallest systems around there are so many amazing things you could do with the Raspberry Pi if it was self-powered and portable. Introducing PiJuice! A fully uninterruptible power supply (UPS) that will always keep your Raspberry Pi powered. The PiJuice HAT is a super-easy way to add a battery backup to Raspberry Pi.

Our revolutionary PiAnywhere technology contained in every PiJuice HAT - is the best way to take your Pi off the grid! The real time clock (RTC) on board will let your Pi know what time it is even with no power input or internet connection. Alongside this is an integrated microcontroller (MCU) chip which will manage soft shut down functionality and a true low power deep sleep state and intelligent startup.

You will be able to always keep track of the charge levels and other info with the two built-in tri-coloured RGB LEDs, trigger events and scripts with the thre programmable buttons and since the PiJuice will use up to just five of your GPIO pins (just power and I2C), the rest are free to diversify your project. The stacking header allows you to continue to use your existing HATs and add-ons with PiJuice.

[...]

Features

• Onboard 1820 mAh off the shelf Lipo / LiIon battery for ~4 to 6 hours in constant use! (with support for larger Lipo Battery of 5000 or 10,000 mAH+ to last up to 24 hrs +)
• A Full Uninterrupted / Uninterruptible Power Supply Raspberry Pi UPS HAT rechargeable battery solution.
• Our PiJuice Raspberry Pi UPS solution works with any Raspberry Pi with 40 GPIO Pins
• Integrated Real-Time Clock
• Rechargeable battery for the Raspberry Pi
• Onboard intelligent on/off switch
• Low power deep-sleep state with wake on interrupt/calendar event
• Programmable multi-colored RGB led (x2) and buttons (x3) with super simple user-configurable options
• Hardware watchdog timer to keep your Raspberry Pi on and working in mission-critical remote applications
• Our revolutionary PiAnywhere technology - the best way to take your Pi off the grid!
• Full power management API available to Raspberry Pi OS with auto shutdown capability when running low on batteries
• Raspberry Pi HAT compatible layout, with onboard EEPROM for easy plug and play operation
• Low profile design to fit inside lots of existing Raspberry Pi cases!
• Enhanced graphical user interface (GUI) available for easy install (via APT)
• Customisable scripts for enhanced flexibility and a full report of battery status
• All GPIOs available via stackable header for ease of expandability and connectivity
• Charge via on-board micro USB or via the Raspberry Pi micro USB (or from onboard pin headers)
• Batteries can be charged from different type of sources and voltages
• Replace the battery without downtime. Compatible with any single cell LiPo or LiIon battery
• Fully CE and FCC tested design. Battery safety tested also.