A Node.js script that follows the transaction amounts, converted to USD, for a given account (here customized for Bitstamp).

websocket_subscribe_account_txn.js

var WebSocket = require('ws');
var moment= require('moment');
var yaml = require('js-yaml');
var fs   = require('fs');

try {
  var doc = yaml.safeLoad(fs.readFileSync('rates.yml', 'utf8'));
  yen_value=doc["EUR"];
  console.log(yen_value);
} catch (e) {
console.log(e);
}

function convert_to_usd(curr,value) {
        if (curr==="BTC") {
          rate=parseFloat(doc["BTC"]);
          console.log("BTC_value")
          to_dollar=value*rate;
          console.log(to_dollar);
          value=to_dollar;
        } 
        else if (curr==="CNY") {
          rate=parseFloat(doc["CNY"]);
          console.log("CNY_value")
          to_dollar=value*rate;
          console.log(to_dollar);
          value=to_dollar;
        }
        else if (curr==="MXN") {
          rate=parseFloat(doc["MXN"]);
          console.log("MXN_value")
          to_dollar=value*rate;
          console.log(to_dollar);
          value=to_dollar;
        }
        else if (curr==="KRW") {
          rate=parseFloat(doc["KRW"]);
          console.log("KRW_value")
          to_dollar=value*rate;
          console.log(to_dollar);
          value=to_dollar;
        }
        else if (curr==="EUR") {
          rate=parseFloat(doc["EUR"]);
          console.log("EUR_value")
          to_dollar=value*rate;
          console.log(to_dollar);
          value=to_dollar;
        }
        else if (curr==="JPY") {
          rate=parseFloat(doc["JPY"]);
          console.log("JPY_value")
          to_dollar=value*rate;
          console.log(to_dollar);
          value=to_dollar;
        }
  return value;
}

var ws = new WebSocket('wss://s1.ripple.com:443/');
var bitstamp = "rvYAfWj5gh67oV6fW32ZzP3Aw4Eubs59B";
var account = bitstamp;
var sum=0;
var time_start=moment();

var info_subscribe={
  command: "subscribe",
  accounts: [bitstamp]
};

ws.on('open', function() {
    ws.send(JSON.stringify(info_subscribe));
});

ws.on('message', function(data, flags) {
  var mom=moment().format('HH:mm:ss');
  console.log(mom);
  words=JSON.parse(data);
  var tx=words["transaction"];
  if (tx) {
    var results=tx["hash"];
    var taker=tx["TakerGets"]
    if (taker) {
      console.log(taker);
      var curr=taker["currency"];
      var val=taker["value"];
      var longval=JSON.stringify(val);
      var cline=curr + ' ' + longval;
      if (typeof curr != 'undefined' && typeof longval != 'undefined') {
        console.log(cline);
        console.log("raw units");
        quoteless=longval.replace(/['"]+/g, '');
        var value=parseFloat(quoteless);
        console.log(value);
        value=convert_to_usd(curr,value);
        sum += value;
        var now=moment();
        var time_diff=now.diff(time_start, 'minutes', true);
        console.log("-------------total amount spent---converted to USD");
        console.log(sum);
        console.log("-------------bitstamp fee profit------------------");
        console.log(sum*parseFloat(doc["BIT"]));
        console.log("-------------time passed in mins------------------");
        console.log(time_diff);
        console.log("--------------------------------------------------");
      };
    }
  } 
});