Although it's probably a long overdue addition for some, the folks from Bittorrent have now updated their Android torrent client µTorrent to offer a WiFi only download option. Previously, when using the app you ran the risk of blowing through your entire data plan or racking up overage charges by leaving some torrents running, but no more. You'll now be able to set it to download over WiFi only and never really worry about it.
In addition to that change, there is also some unspecified stability improvements in this release.
Hit the Google Play Store link above to grab the latest version.