Are there any best practices and/or tools for 'nohup' monitoring?
I'm not sure it's a best practice but what I would do is using filebeat to read the log in near real time and push it to ElasticSearch.
AWS provides an ElasticSearch Service which can save you from this part.

The drawback of using filebeat directly to elasticsearch is that the time of events will be the time the prospector read them and if your logs have a timestamp they can be "ingested" in different order than produced (from multiple workers).

You can add Logstash inbetween, sending from filebeat to logstash and then to elasticsearch. Logstash is able to interpret your logs and split them into fields to search again, in the same manner you can parse your date in log so events will be stored with a correct timestamp.

You may use logstash directly to read the logs, but it's quite heavy on resources so I would keep it separated to no impact the workers.

If you buy a license from x-pack you can add alerts on messages directly from elasticsearch.

If you want to save you from the burden of maintaining logstash there's services like logmatic.io which provides you with the full stack, you just have to push your logs and a bunch of parsing are handled from stock.