Mobile app for iot ble button to send gps location when pushed

I am looking for experienced mobile app developers to create an app for an IoT BLE button. The app will need to be developed for both iOS and Android and the user interface simple but nice. The app should be able to send out the GPS location of the user when the button is pushed to a pre-selected list of recipients from the contacts. As for integration with devices, it needs to connect to a bluetooth button, I can share the specifics later — I'm open to any advice the developer can provide on that front. As for existing databases, I do not have one. The developer will need to set that up as well. The project should be both time- and cost-efficient.