Cross platform app in Flutter with Web front end for different user.
If you are really comfortable in below mentioned technologies then bid :
Frontend: ReactJS or Vuejs
Backend: Java microservice(Spring, Dagger, OpenAPI, Swagger Hibernate, MySQL/Postgress,Rest,Jwt,Auth0 ,Elasticsearch, API gateway, Push Notification etc)
MobileTech: Flutter/React Native or in case of native Java and swift,Sqlite, Bluetooth Connectivity
Monitoring: Grafana, promethus