OpenSim is an open source alternative to SimPholders, written in Swift 3. If you are looking for sources with Swift 2, please check out the swift-2.2 branch.

You can visit the latest release to grab a compiled version. (Warning: It's not code-signed.)

• Parsing results from xcrun command rather than device_set.plist file (thank @bradvandyk)
• Watch for changes from simulators directory and reload dynamically
• Filter out empty simulators
• Better UI
• Other functionalities like uninstalling apps or resetting data