I maintain the GPSTest app on Google Play, which is open-source on Github.
I'm actively interested in adding Galileo support in the app, but to do this I need to know what IDs the Galileo satellites show up as in the Android platform. And, this requires that there be some agreement between Galileo hardware manufacturers of those IDs - see Is there an industry-standard official mapping of Galileo satellites to global "PRN”/ID values?.
I personally haven't seen any Android devices reporting Galileo satellites yet - as soon as I do, and I'm able to find out the ID range agreed upon for Galileo, I'll add support to GPSTest.
If you have an Android device that supports Galileo and you're willing to help identify the range, please comment on this Github issue.
EDIT Sept. 19, 2016
For Android 7.0 (N) and higher, Google has added a new API in Android that allows apps to explicitly determine the GNSS type of each satellite for the following GNSS constellation (from https://developer.android.com/reference/android/location/GnssStatus.html).
I'll work on adding this to GPSTest, and will update my answer when it's live.
EDIT Oct. 6th, 2016
I have a working build of GPSTest that I believe should support Galileo. If you have and a device with Galileo support (i.e., hardware), please comment on the below pull request on Github - I'd love to get feedback to know if it works!
EDIT Oct. 26, 2016
GPSTest v2.1.8 and up now supports Galileo! Download on Google Play at https://play.google.com/store/apps/details?id=com.android.gpstest. Supports all devices with Android 7.0 (N) that have a Galileo-compatible chipset. Support for Galileo on Android 6.0.1 (M) and lower will depend on your device OEM.
So far users have confirmed that they are able to see Galileo satellites using GPSTest on the following devices:
BQ Aquaris X5 Plus (See this post)
Huawei Mate 9 (See this post)
Samsung Galaxy S8 and S8+ (See this post and official specs which say "Location (GPS, Galileo, Glonass, BeiDou) *Galileo and BeiDou coverage may be limited.")
OnePlus 5 (Android 7.1.1 / OxygenOS 4.5.8) (See this post)
Huawei P10 (See this post - Android 7.0, firmware version L29C432B171)
OnePlus 5T (See this post)
EDIT Mar. 26, 2018
The site UseGalileo.eu (by the EU GSA that operates Galileo) now has a list of devices and chipsets that support Galileo: