I've got this error before. It would say "File Not Accepted: The target device claims it will not accept a file of the type you are trying to send" or "Error, device does not accept files of this type" This is because of not having permission to accept this file. You have to add permission in the Manifest file.
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
Under the activity enter something like this!
<activity name="BluetoothActivity">
<intent-filter>
<action android:name="android.intent.action.VIEW" />
<category android:name="android.intent.category.DEFAULT" />
<category android:name="android.intent.category.BROWSABLE" />
<data android:mimeType="*/*" />
<data android:pathPattern="*.*\\.gpx" />
</intent-filter>
</activity>