This application has not been updated for a year, and I don't plan to update it for the time being because I don't have time to do so right now. You can still use it, and it should still give pretty good results, but keep in mind it is outdated. Completely offline itinerary calculation in Paris' underground Free, without any ad, and will remain so.
You can get the .apk installation package of Metro 1.65 free of charge and read users' reviews on Droid Informer. This file size doesn't exceed 132 KB and the app can be launched flawlessly on Android 1.6 and higher. According to the antivirus report, this application is safe and secure. The tool has been originally developed by PKH and it is included in the Maps & Navigation category.
The most recent update of Metro was released on Apr 20, 2011 and the app was downloaded by over 100K users. According to the latest info, this application is rated 4.1 on Google Play.