I'm not going to explain how to get the emulators configured, those are well documented, but rather just give the command to launch them.
Android Emulator:
~/Library/Android/sdk/tools/emulator -list-avds
~/Library/Android/sdk/tools/emulator -avd {AVD}IOS Emulator:
xcrun simctl list devicetypes
xcrun simctl list runtimes
xcrun simctl create {devicetype} {runtime}
xcrun simctl boot {UID}
open /Applications/Xcode.app/Contents/Developer/Applications/Simulator.app