Oracle Failsafe is a mostly unknown Oracle Product. I am working with this product since a short period of time, and must say it is a perfect and cheap High-Availability Solution for Oracle-Database.
"How cheap is it?"
Hmmm it costs NOTHING 
you are allowed to use it if you have an oracle database. Of course, it costs you Microsoft-Licenses (Microsoft Enterprise Server) but no additional Oracle licenses.
"Do i need additional Database Licenses the same way i use the Oracle-RAC (Real Application Cluster)"
No, There is no additional License necessary because there is always just one Database active, read more about it in the Oracle Software Investment Guide.
"How does it work?"
Failsafe is a peace of software that takes care of your Oracle Database on a Microsoft Cluster. If one Database-Server goes down for any reason (fire, maintenance etc.) the database gets switched on an other server (called "node" in a clustered environment).
"How long does this switching take?"
It takes below an minute, we measured between 20 and 30 seconds (the listener and the database gets restarted).
Here a screenshot of how it looks like:
In this example (from the manual) you can see the Cluster FS-150 and two nodes (servers) FS-151 and FS-152.
Hee you can get more information about it:
