Spark Hello World

// Read temperature
// -----------------

// Create a variable that will store the temperature value
int temperature = 0;

void setup()
{
  // Register a Spark variable here
  Spark.variable("temperature", &temperature, INT);

  // Connect the temperature sensor to A7 and configure it
  // to be an input
  pinMode(A7, INPUT);
}

void loop()
{
  // Keep reading the temperature so when we make an API
  // call to read its value, we have the latest one
  temperature = analogRead(A7);
}The returned value from the Core is going to be in the range from 0 to 4095. You can easily convert this value to actual temperature reading by using the following formula:
voltage = (sensor reading x 3.3)/4095
Temperature (in Celsius) = (voltage - 0.5) X 100
The API request will look something like this:
GET /v1/devices/{DEVICE_ID}/temperature

# EXAMPLE REQUEST IN TERMINAL
# Core ID is 0123456789abcdef
# Your access token is 123412341234
curl -G https://api.spark.io/v1/devices/0123456789abcdef/temperature \
  -d access_token=123412341234