When you buy your OBi110 and register it on the Obihai network, you will automatically get a free softphone number. This enables you to bridge calls from your Android phone through the OBi110 using any service (e.g. PSTN) that exists on your OBi110. This uses the free android app - OBiON for Android. Warning! This app has not been updated for years and may not work well for you on your android phone - see a whole section on this forum - OBiON for Android.
If the above does not work so well for you, then there are many other free softphones for Android that can be used in conjunction with free voip services to bridge between your android phone and the OBi110. CSipSimple, Zoiper, Linphone etc are all possible choices.
The simple answer to your question is "yes". However, you might need some fine tuning to get a good reliable bridge working between your android phone and the OBi110.