cordova.ts

const promisifyCordova = (pluginName:string, methodName:string) => {
  return (...args) => {
    return new Promise((resolve, reject) => {
      cordova.exec(resolve, reject, pluginName, methodName, args);
    })
  }
}

const observablifyCordova = (pluginName:string, methodName:string, cleanUpMethodName?:string) => {
  return (..args) => {
    return new Observable(observer => {
      cordova.exec((val) => observer.next(val), (err) => observer.error(err), pluginName, methodName, args);
      return () => {
        if(cleanupMethodName){
          cordova.exec(noop, noop, pluginName, methodName);
        }
      }
    })
  }
}

let getPicture = promisifyCordova('camera', 'getPicture');

getPicture(options).then(...);

let GeoLocation = observablifyCordova('geolocation', 'startWatch', 'stopWatch');

let watcher = GeoLocation.subscribe(...);

//later
watcher.unsubscribe(...);