We love this smart idea! A voltage regulator with the standard 7805 pinout, with 5V output voltage, and a huge advantage: It replaces the typical voltage drop regulator, which needs a much higher input voltage of 7-35V. This Step-Up converter only needs the input voltage of 0.9 to 5V, for its 5V output voltage. When you needed a 9V power supply or 4 AA/AAA batteries, to have the voltage high enough to convert it to 5V, you can now just use a single battery, or 2 or 3, or even 1 lithium cell with 3.7V, depending on the current you need.
This little module replaces the 7805 voltage regulator 1:1, to switch from power supply operation to battery operation.
The DC-DC converter does not need any heat sink, and also the capacitors you will find on in- and output of a 7805 are not necessary anymore.