This app was mentioned in 4 comments, with an average of 2.50 upvotes
https://play.google.com/store/apps/details?id=com.synology.DSdownload
It's Synology mobile phone app for the Download Station (the app you use to download the torrents in the NAS).
I don't use IPhone so not sure if it's called the same there, but i guess it should at least have some equivalent app
It's in the Google Play store - https://play.google.com/store/apps/details?id=com.synology.DSdownload
AppShopper still has it listed too (no idea where it gets it's listings from) - http://appshopper.com/utilities/ds-download
This it not a problem at all.
1: There's a torrent client built into the NAS or downloadable from package center (the "app store of Synology").
2A: For Chromium browsers, get the addon Synology Download Station and configure it to connect to the NAS.
2B: For phones download DS get for iPhone OR DS get for Android
Note that you need to forward some ports in order for your NAS to work with the addons outside of your home network.
Route VPN through NAS, remotely access NAS and queue downloads while at work or via mobile app (iOS), come back home to a finished download. This is way more efficient than sitting around waiting at home.