You need it to be reliable, and you need to retrieve the results when you want it.:
My approach would be to set up a VPS on amazon, a free tier linux server would do, the cost (directly billed to you via Amazon, I can help to set it up) would be low. This won't be the cheapest option but it will be reliable and it will be available from anywhere. ( I could also deliver code which you can run yourself on a WAMP or LAMP environment. )
This system would focus on saving every new tweet from the users you specified. results will be saved on a mysql db, and via a web interface you will be able to retrieve the results and download csv files.
In this case I would advise to use the ‘streaming API’.But I must warn you that it is not possible to retrieve all historical results, my solution would only monitor and save data if it encounters it in real time, that means that if you wish to monitor a specific user, it will save data after the user posted tweets. It would also be possible to include some historical results. I could work on that too.
Moreover I have to warn you that there are rate limitations when using the Twitter API’s.
Please let me know what type of solution you are looking for, I could also just send a daily update by e-mail for a limited time for a better price.
Technology: Linux server, Apache2, PHP, MYSQL.