This is a very hard question. I have never been counting how much time I spent in developing the blessTags application. With the release of each new version, the number of code lines that the new version of the application has it is counted and presented to the users - please see the blessTags version history section. This indicator, the number of code lines of the blessTags application, it is a very good reference for the efforts made in developing the application. But that's not all. Testing the newly developed features, testing their integration with the rest of the application also takes a lot of time.
In order to highlight these efforts (made in the testing phase of the application), but also those deployed in the development of the blessTags application, I think an image is much more exciting.
In the below figure, I present all the coins batteries (CR2032) depleted in the last 6-8 months in the development phase and testing phase of the blessTags application with different types of the SensorTags.