A simple sketch for detecting a button press (for example, a doorbell) that calls a web page to send a text message. The onboard RGB LED will be red when nothing is happening. It turns green as it makes the web request, and then turns blue for 1 second after the request.

smartDingDong.cpp

int ddl = 0;             // Ding dong last millis()
int btnpin = D0;         // "Button" pin
const int ddd = 15000;   // Time until button can be activated again

void setup() {
    pinMode(btnpin, INPUT_PULLUP);

    RGB.control(true);
}

void loop() {
    if(digitalRead(btnpin)==LOW)
        dingdong();
    else
        RGB.color(255, 0, 0);
}


void dingdong() {
    if(ddl==0 || (ddl+ddd)<millis()) {
        ddl = millis();
        
        RGB.color(0, 255, 0);
        httpGetRequest("IP_ADDRESS", "HOSTNAME", 80, "/path_to_doorbell/");
        RGB.color(0, 0, 255);
        
        delay(1000);
    }
}


void httpGetRequest(char *ip, char *hostname, int port, char *url) {
    String line;
    char cline[100];
    
    TCPClient client;
    client.connect(ip, port);

    line = "GET " + String(url) + " HTTP1/.1";
    line.toCharArray(cline, 100);
    client.println(cline);

    line = "Host: " + String(hostname);
    line.toCharArray(cline, 100);
    client.println(cline);
    
    line = "Content-Length: 0";
    line.toCharArray(cline, 100);
    client.println(cline);
    
    client.println();
    client.flush();
    client.stop();
    
    delay(250);
}