As the description of this project already describes, TapV2's main purpose is to be a playground of various sensors and other bits of data processing. Not for any specific reason, mind you - a lot of these elements here are just sensors we'd love to try out, or that we might find useful once a year and would like to have on hand.

Some of them may even be genuinely useful!

Right now we are still in the process of squishing the sensors we already selected as close together as possible and might go ahead and add one or two more if we find them interesting enough.
Perhaps the comments could even recommend something to add to the arsenal.

For now, the list is already quite capable.
Going from left to right we have:

• A pulse oximeter that can measure pulse and SpO2 levels when the user places their finger on it.
• An LSM6DSM 6-axis gyro (although almost all MEMS gyros are out of stock for a few years - this one might have to be retrofitted somehow, or salvaged from another board)
• An APDS-9500 gesture sensor. Although simple looking at first, this little device sports a 60x60 pixel IR array that can act like a rudimentary camera, potentially even enough to read QR codes! 
  It is the main motivation for this board, and will hopefully serve us well.
• A BME680 air quality sensor. Aside from the standard humidity, temperature and pressure, the 680 also reads "Volatile Compounds" that correlate roughly to how used-up the air is, and can give warnings about low air quality.
• A I2S MEMS microphone, used for simple whistle command input as well as Fourier Frequency analysis. Being able to isolate that one frequency that's annoying you should always be easy.
• And STM ToF LIDAR with about 1m range in good conditions. Not only will it replace a slide rule, it could also be used to automatically measure vibrations up to 50Hz!

The very rightmost components are for communication, such as a "On-Ground" WiFi antenna chip, and a IR module.

One last potential candidate as sensor is an ambient brightness and UV meter, to warn about excessive solar radiation, however the only part we could find for this has a big "Not recommended for new design" label across the datasheet, so it's a "maybe".

Oh, and those squares that are lined up next to every sensor module?
Those are 1.8mm sized NeoPixel clones, to illuminate each sensor's status and readouts - mainly to look flashy and interesting.

Let's see how hard it is to wire everything up. There is a reason why we chose automated assembly and 4-layer boards right from the conception of the project!