Currently there are two unofficial Miiverse apps available on Android through Google Play. Check them out here and here. The former is made by IBAI SAINZ-AJA and the latter is made by LANTERNWARE. The one from Lanternware is more inclusive as the application includes the Nintendo Youtube channel for trailers and Nintendo Directs, as well as official Nintendo tweets to keep users up to date while the one from Ibai Sainz-Aja only accesses Miiverse. Access to Miiverse through both apps is in beta as posts cannot be made, although you will be able to reply and give +Yeahs.