Super-tightly PCB-mounted WS2812B addressable LEDs, available in white or black trim.
The WS2812B is a very convenient addressable LED. Hook up a string of leds with 3 wires (power/ground/signal), clock in the appropriate data, and then they all shine their assigned color. They're available in all sorts of configurations, and this one is ideal for wearables or single indicators where a strip isn't convenient.
Each 5050 form-factor LED is mounted on a single round PCB matching the LED's trim color (black or white). Since they are tightly designed, there are no mounting holes to sew or screw to. They have to be glued or mechanically mounted to your project. We used them to great effect with our superflex wire as accent twinklers on a graduation dress.
Note: Our general experience with WS2812B LEDs shows you really should use a minimum 560 ohm resistor on the output of your microcontroller (like an Arduino) to the first LED of the chain. We've blown up a good number of the first LEDs in a chain due to overdriving the input. After the first LED, wire them together point-to-point as normal.