Senior Chess is written by Leen Ammeraal from Netherlands. It's relatively an old app but it never stopped progressing since years. The latest update to 1.82 is now available at GOOGLE PLAY.
If you've never used Senior Chess, note that you will like its ease of use especially. It has a clean and readable layout without complicated menus. It's simply a suitable mate for any chess player above average.
Regarding the strength, it's not a monster for sure. I never had the opportunity to play manual games vs UCI engines we know from Rapidroid. I would guess something between 1800 and 2000 ELO.