Add in Geolocation component

mobile/src/ui/Geolocation.js

@@ -0,0 +1,36 @@
+import React, { Component } from "react"
+import { Image, View } from "react-native"
+import PropTypes from "prop-types"
+import autobind from "autobind-decorator"
+
+export class Geolocation extends Component {
+  static propTypes = {
+    onUpdate: PropTypes.func.isRequired,
+  }
+
+  constructor(props) {
+    super(props)
+    this.watchId = -1
+  }
+
+  componentDidMount() {
+    navigator.geolocation.getCurrentPosition((position) => {
+      this.props.onUpdate(position)
+      this.watchId = navigator.geolocation.watchPosition((position) =>
+        this.props.onUpdate(position)
+      )
+    })
+  }
+
+  componentWillUnmount() {
+    if (this.watchId !== -1) {
+      navigator.geolocation.clearWatch(this.watchId)
+      navigator.geolocation.stopObserving()
+      this.watchId = -1
+    }
+  }
+
+  render() {
+    return null
+  }
+}