feat(plugin): add functionality to device motion plugin

src/plugins/devicemotion.ts

@@ -1,5 +1,38 @@
 import {Plugin, Cordova} from './plugin';
 
+export interface accelerationData {
+
+  /**
+   * Amount of acceleration on the x-axis. (in m/s^2)
+   */
+  x : number,
+
+  /**
+   * Amount of acceleration on the y-axis. (in m/s^2)
+   */
+  y : number,
+
+  /**
+   * Amount of acceleration on the z-axis. (in m/s^2)
+   */
+  z : number,
+
+  /**
+   * Creation timestamp in milliseconds.
+   */
+  timestamp : any
+
+}
+
+export interface accelerometerOptions {
+
+  /**
+   * Requested period of calls to accelerometerSuccess with acceleration data in Milliseconds. Default: 10000
+   */
+  frequency? : number
+
+}
+
 /**
  * Requires Cordova plugin: `cordova-plugin-device-motion`. For more info, please see the [Device Motion docs](https://github.com/apache/cordova-plugin-device-motion).
  *
@@ -17,10 +50,45 @@ import {Plugin, Cordova} from './plugin';
 })
 export class DeviceMotion {
 
+  /**
+   * Get the current acceleration along the x, y, and z axes.
+   * @returns {Promise<any>} Returns object with x, y, z, and timestamp properties
+   */
+  @Cordova()
+  static getCurrentAcceleration () : Promise<accelerationData> {
     // This Promise is replaced by one from the @Cordova decorator that wraps
     // the plugin's callbacks. We provide a dummy one here so TypeScript
     // knows that the correct return type is Promise, because there's no way
     // for it to know the return type from a decorator.
     // See https://github.com/Microsoft/TypeScript/issues/4881
+    return new Promise<accelerationData>((res, rej) => {});
+  }
+
+  /**
+   *
+   * @param options
+   * @returns {Observable<accelerationData>}
+   */
+  @Cordova({
+    successIndex: 0,
+    errorIndex: 1
+  })
+  static watchAcceleration (options? : accelerometerOptions) : Promise<accelerationData> {
+    // This Promise is replaced by one from the @Cordova decorator that wraps
+    // the plugin's callbacks. We provide a dummy one here so TypeScript
+    // knows that the correct return type is Promise, because there's no way
+    // for it to know the return type from a decorator.
+    // See https://github.com/Microsoft/TypeScript/issues/4881
+    return new Promise<accelerationData>((res, rej) => {});
+  }
+
+  /**
+   * Stop watching the Acceleration referenced by the watchID parameter.
+   * @param watchID The ID returned by watchAcceleration method
+   */
+  @Cordova({
+    sync: true
+  })
+  static clearWatch(watchID : any) : void {}
 
 }