Yes you can, see this example: http://www.b4x.com/android/forum/th...p-to-your-b4j-server-over-the-internet.37201/
You'll have to:
1. make a static IP account somewhere ( like "No-IP" )
2. write the b4j application which will supply the key, with service to answer the calls.
3. Create an HTML page to show the form above.
There are more examples in the forum.