I had been writing programs on an Arduino UNO WiFi Rev2, but found the BLE library was using up all the memory, leaving almost nothing for other libraries or program variables. So I got the Arduino Nano 33 BLE as a replacement and am very impressed. It has a surprisingly powerful processor with plenty of memory, yet the physical size of the board is tiny and it is very lightweight. Getting one without headers would allow it to be even more light and compact (I might even snip the header pins off once I'm sure I don't need them). Using 3.3V and having a fairly low power demand also makes it easier to power from a battery. All in all, this makes the Nano 33 BLE a great device for experimenting with wearable technology. It even has a built-in acceleromoter / IMU. BLE is not very fast for sending large amounts of data (it is not really designed for that purpose), but there is enough RAM on this module to allow a decent amount of data buffering. This allows me to collect short bursts of high resolution IMU data and stream them sedately to a laptop over BLE. The photo shows it powered from a Li-Ion 18650 battery in a cheap battery management module I picked up on eBay. I need to find a smaller and lighter power solution because the battery currently dwarfs the Nano 33 BLE.