If you are looking for a no-frills depth of field calculator app for Android, you can do much worse than giving the DoF Calculator a try. Released under the GPLv3 license, this app has the virtue of doing one thing well: calculating the depth of field and limit values for any given camera model, lens focal length, and distance to the subject combination.
DoF Calculator is not available in the Google Play Store, but you can either sideload it using the latest APK package from the project’s website, or install the app through the F-Droid market. Unsurprisingly, DoF Calculator is very straightforward in use: pick the desired camera model, focal length, aperture, and the distance to the subject, and tap the Calculate button. The app then returns three values: near and far limits along with the total depth of field.