Home appliance suggestion?

We recently expanded our house. It has gotten really big.. So big that every family members are in different rooms and it is so hard to gather everybody for dinner, prayer or anything. My mom calls our phone or sometimes literally yells until her throat gives out. How to tackle this situation? Any useful home appliances or products?walkie talkies? Roombell? Speaker? Idk which will be good. It has to be low budget too.