Hi, 
I am on the same way. I am trying to receive measurements from a digital caliper but I can not pass the network key to acquireChannelOnPrivateNetwork method, because it accepts 16 byte network key. My key is only 8 byte.
Modified parts of ChannelService.java:
// Network key declaration
    private static final byte[] NETWORK_KEY = new byte[]
            {(byte) .....}; //  Network Key
    private NetworkKey mNetworkKey = new NetworkKey(NETWORK_KEY);
...
// Try to acquire a private channel with 8 byte Network key
            try {
               mAntChannel = mAntChannelProvider.acquireChannelOnPrivateNetwork(this, mNetworkKey);
            } catch (RemoteException e) {
                die("ACP Remote Ex");
            }
            catch ( UnsupportedFeatureException e) {
                Toast.makeText(this, "Unsupported Feature", Toast.LENGTH_SHORT).show();
                die("ACP Unsupported Feature Ex");
            }
            catch ( IllegalArgumentException e) {
                Toast.makeText(this, "ACP Illegal Argument Ex" + e, Toast.LENGTH_SHORT).show();
                die("ACP Illegal Argument Ex" + e.toString());
            }
I get "IllegalArgumentException: Received network key that is null or has invalid length" when I pass 8 byte Network key.
How can I pass the 8 byte key?
Regards, 
Szabolcs