I nearly bought this kind of thing, but then realised I had all the parts I needed to make it myself, which is half the fun, right?!

 

This video shows it in action;

 

 

What I'm using in this build is;

 

PartApprox Price
24 LED Ring£2
Arduino Nano£1.75
Breadboard, button, potentiometer, and wires£1.25

 

The components are wired up like this;

 

 

And here's the code (uses the Adafruit neopixel library);

 

#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
  #include <avr/power.h>
#endif

#define PIN 6 // pin on the Arduino is connected to the LED ring
#define NUMPIXELS 24 // Number of pixels on the LED ring
#define POT_PIN 0 // Potentiometer pin
#define BUTTON_PIN 2 // Button pin

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

int showType = 0;
bool oldState = HIGH;

void setup() {

  pinMode(BUTTON_PIN, INPUT_PULLUP); // Declare pushbutton as input
  pixels.begin(); // This initializes the NeoPixel library.
  
}

void loop() {

  // Read the potentiometer value and translate to how many pixels we want to illuminate
  int value = analogRead(POT_PIN);
  value = map(value, 0, 1023, 0, 25);

  // Switch colours if the button is pressed
  bool newState = digitalRead(BUTTON_PIN);
  if (newState == LOW && oldState == HIGH) {
  delay(20); // Short delay to debounce button.

  // Check if button is still low after debounce.
  newState = digitalRead(BUTTON_PIN);
  if (newState == LOW) {
// Cycle through different colour schemes
  showType++;
  if (showType > 8) showType=0;
  }
  }
  oldState = newState; // Set the last button state to the old state.
  
  uint32_t color = pixels.Color(255,255,255); // default to white when first booted

  if (showType==1) color = pixels.Color(0,0,255); // blue
  if (showType==2) color = pixels.Color(0,255,0); // green
  if (showType==3) color = pixels.Color(255,0,0); // red
  if (showType==4) color = pixels.Color(0,127,255);
  if (showType==5) color = pixels.Color(255,127,0);
  if (showType==6) color = pixels.Color(255,0,127);
  if (showType==7) color = pixels.Color(0,255,255);
  if (showType==8) color = pixels.Color(127,127,255);

  // Illuminate X pixels depending on how far the potentiometer is turned
  for(int i=0;i<NUMPIXELS;i++){
  if (i<value) {
  pixels.setPixelColor(i, color);
  } else {
  pixels.setPixelColor(i, pixels.Color(0,0,0)); // Don't show anything
  }
  }
  
  pixels.show(); // This sends the updated pixel configuration to the hardware.
 
}

 

And here's the end result!