As it was given in the Manning website, knowledge in Java is helpful. It means the enterprise edition of Java. Right?
No. Android is based on Java SE 5 with a few libraries added (like HttpClient and the Android GUI toolkit) and a few libraries removed (like AWT and Swing).
Is there anything else I need to do to glue the application across the gadgets? Like a configuration file etc.,
An app consists of a single .apk file that is deployed on all devices. It contains all the resources necessary to work on differently enabled devices (like different screen sizes, landscape/portrait screens etc.). Differentiation happens by feature, not by device maker or model.
How do you measure the performance of an Android application?
The same way you'd do it for any other application. Of course, it depends on what -exactly- you mean by "performance".
Check this out: http://code.google.com/p/android-scripting/
. JavaFX is tied on Swing and thus won't work.
How do I differentiate Android with Java ME? Is it just a technology/framework running on top of Java ME?
Android is independent of JME. JME apps won't run on Android devices and vice versa.