Send a short email/text message/sms with Paid Memberships Pro Membership Checkout.

my_pmpro_checkout_notifications.php

/*
	Send a short email with every purchase.
*/
function my_pmpro_checkout_notifications($user_id, $order)
{
	global $wpdb;

	//email address to send to - for sms/text message, see http://www.emailtextmessages.com/ for your carrier's format
	$email = "4444444444@vtext.com, 5555555555@vtext.com";

	//only send for levels 1 and 2 - remove lines 12 to 14 to include all levels
	$notification_levels = array(1,2);
	if(!in_array($order->membership_id, $notification_levels))
		return;

	//get user info
	$user = get_userdata($user_id);

	//get level info
	$level = pmpro_getLevel($order->membership_id);

	//get total order value for today
	$today = $wpdb->get_var("SELECT SUM(total) FROM $wpdb->pmpro_membership_orders WHERE status NOT IN('refunded', 'review', 'token', 'error') AND timestamp >= '" . date("Y-m-d", current_time('timestamp')) . "' AND gateway_environment = '" . esc_sql(pmpro_getOption('gateway_environment')) . "' ");

	//build message
	$subject = "Checkout: " . $level->name;
	$message = $user->display_name . " (" . $user->user_email . "). $" . $order->total . " of $" . $today . " today. ";

	//sweeten it up
	$phrases = array(
		"Nice job!",
		"Way to go!",
		"Keep it up!",
		"Alright!",
		"Sweet!",
		"Awesome!",
		"Woah!",
		"Nice!",
		"Congrats!",
		"Yes!",
	);

	$message .= $phrases[array_rand($phrases)];

	//send it
	if(class_exists('wpMandrill'))
	{
		$message = array(
			'html'=>$message,
			'text'=>$message,
			'subject'=>$subject, //$subject,
			'to'=>$email,
		);
		wpMandrill::sendEmail($message, "", "", false, false);

		//wpMandrill::wp_mail_native($email, $subject, $message);
	}
	else
		wp_mail($email, $subject, $message);
}
add_action('pmpro_after_checkout', 'my_pmpro_checkout_notifications', 10, 2);

This recipe is included in the blog post on "Track Membership Signups and Stats on a Mobile Device" at Paid Memberships Pro here: https://www.paidmembershipspro.com/track-membership-signups-stats-mobile-device/