How can I disable Bluetooth A2DP profiles on the iPhone 4?
The app you are referring to has a manual process you can try, but it is not for the faint of heart: http://blog.ramondeklein.nl/?p=257


  Howto disable A2DP on the iPhone
  
  The interesting directory is
  /var/mobile/Library/Preferences, where
  the iPhone stores the BlueTooth
  settings. These settings are stored in
  the PLIST format, so you need a PLIST
  editor (Mac or PC) or you need to
  convert them by hand. Transfer the
  com.apple.MobileBluetooth.services.plist
  to your computer or you can use iFile
  to edit the file on your iPhone
  directly.
  
  Open the
  com.apple.MobileBluetooth.services.plist
  in your PLIST editor and make sure you
  edit the A2DPService section and store
  the devices you don’t want to use A2DP
  in the UnauthorizeList (without the
  letter “d”). This dictionary will
  probably not exist yet, so you need to
  add it by hand. You need to know the
  MAC address, but it is probably listed
  already in this file.

&lt;key&gt;A2DPService&lt;/key&gt;
&lt;dict&gt;
  &lt;key&gt;State&lt;/key&gt;
  &lt;true/&gt;
  &lt;key&gt;UnauthorizeList&lt;/key&gt;
  &lt;dict&gt;
    &lt;key&gt;00:10:60:D0:91:D0&lt;/key&gt;        &lt;!-- This is the MAC address --&gt;
    &lt;date&gt;2009-08-08T01:00:00Z&lt;/date&gt;   &lt;!-- Timestamp --&gt;
  &lt;/dict&gt;
&lt;/dict&gt;

  
  Transfer the PLIST file back to your iPhone and reboot the device. Once it gets back on,  then the A2DP service should be disabled.