Aside from the Android Studio's built-in feature, there's nice gradle plugin called Gradle Versions Plugin that does exactly what you want, with the benefit of being plain gradle extension, which means being NOT bond to any IDE - just pure Gradle thing.
Gradle Versions Plugin can create reports in human readable plain text form, but can also dump it as JSON or XML which is pretty useful for automated/scripted processing.
Usage is pretty simple. Once added to your gradle file, you just do:
> ./gradlew dependencyUpdates
and it should produce project dependency report that looks like this:
------------------------------------------------------------
: Project Dependency Updates (report to plain text file)
------------------------------------------------------------
The following dependencies are using the latest milestone version:
- com.github.maksim88:PasswordEditText:v0.9
- com.marcinorlowski:webnet-log:1.0.3
- com.nulab-inc:zxcvbn:1.2.2
The following dependencies exceed the version found at the milestone revision level:
- com.hannesdorfmann.fragmentargs:annotation [4.0.0-SNAPSHOT <- 3.0.2]
- com.hannesdorfmann.fragmentargs:bundler-parceler [4.0.0-SNAPSHOT <- 3.0.2]
- com.github.bumptech.glide:glide [3.7.0 <- 3.6.1]
- com.hannesdorfmann.fragmentargs:processor [4.0.0-SNAPSHOT <- 3.0.2]
The following dependencies have later milestone versions:
- com.github.PhilJay:MPAndroidChart [v2.2.5 -> v3.0.1]
- com.android.support:appcompat-v7 [25.1.0 -> 25.1.1]
- com.jakewharton:butterknife [8.4.0 -> 8.5.1]
Generated report file build/dependencyUpdates\report.txt
See docs for extensive usage examples.
NOTE: as of writing this answer (2017-01), versions higher than 0.17.0 produce more output in plan text format, incl. project URLs thus making the whole output bloated.