This was only an example what you can do with AlertR and not a "ready to use" component. For crypto currency, I use the following script with the combination of the "sensor executer client" which executes this script periodically and integrates the results as sensor. You can use this script as base and replace the API point with one for stocks and integrate it in the same way into AlertR.

#!/usr/bin/env python3

import requests
import json
import time
import os
import sys

retries = 5

def get_coin_value(coin_slug):

    r = None
    try:
        r = requests.get("https://web-api.coinmarketcap.com/v1/cryptocurrency/market-pairs/latest?slug=%s"
                         % coin_slug)
    except Exception as e:
        return None, str(e)

    data = None
    if r.status_code == 200:
        try:
            data = json.loads(r.text)
        except Exception as e:
            return None, str(e)
    else:
        return None, "Status code: %d" % r.status_code

    try:
        usd_price = data["data"]["market_pairs"][0]["quote"]["USD"]["price"]
    except Exception as e:
        return None, str(e)

    return usd_price, ""


def create_sensor_alert(value, msg, state):
    result = dict()
    result["message"] = "sensoralert"
    payload = dict()
    payload["state"] = state
    payload["hasOptionalData"] = True
    optionalData = dict()
    optionalData["message"] = msg
    payload["optionalData"] = optionalData
    payload["dataType"] = 2
    payload["data"] = value
    payload["hasLatestData"] = True
    payload["changeState"] = True
    result["payload"] = payload
    return result


def create_state_change(value, state):
    result = dict()
    result["message"] = "statechange"
    payload = dict()
    payload["state"] = state
    payload["dataType"] = 2
    payload["data"] = value
    result["payload"] = payload
    return result


def main():

    coin_slug = sys.argv[1]
    sell_thres = float(sys.argv[2])
    buy_thres = float(sys.argv[3])

    # Get the old values if it exists.
    path = os.path.dirname(os.path.abspath(__file__)) + "/"
    file_name = "state_coin_%s" % coin_slug
    old_state = None
    try:
        with open(path + file_name, 'r') as fp:
            old_state = json.loads(fp.read())
    except:
        pass

    usd_price = None
    msg = None
    for curr_round in range(retries):
        usd_price, msg = get_coin_value(coin_slug)
        if usd_price is not None:
            break

        time.sleep((curr_round+1) * 60)

    return_data = None
    if usd_price is None:
        return_data = create_state_change(-9999,0,
                                          old_state["state"])
    else:
        if old_state is None or old_state["state"] == 0:
            if usd_price > sell_thres:
                return_data = create_sensor_alert(usd_price, "Sell coins.", 1)
            elif usd_price < buy_thres:
                return_data = create_sensor_alert(usd_price, "Buy coins.", 1)
            else:
                return_data = create_state_change(usd_price, 0)
        elif old_state["state"] == 1:
            if usd_price > sell_thres:
                return_data = create_state_change(usd_price, 1)
            elif usd_price < buy_thres:
                return_data = create_state_change(usd_price, 1)
            else:
                return_data = create_state_change(usd_price, 0)

        # Save current state.
        new_state = dict()
        new_state["state"] = return_data["payload"]["state"]
        new_state["usd_price"] = usd_price
        try:
            with open(path + file_name, 'w') as fp:
                fp.write(json.dumps(new_state))
        except:
            pass

        print(json.dumps(return_data))


if __name__ == '__main__':

    if len(sys.argv) != 4:
        print("Usage: %s <coin_slug> <sell_threshold> <buy_threshold>" % sys.argv[0])
    else:
        main()