Desde que eu saiba, não há API para o método "Ativando AP", mas posso usar a reflexão para ativá-la. Aqui é o que eu faço

wifi_manager = (WifiManager) this.getSystemService(HotSpot_TrisActivity.this.WIFI_SERVICE);
btnEnableAP = (Button)findViewById(R.id.btnEnableAP);

btnEnableAP.setOnClickListener(new View.OnClickListener() 
{

   @Override
   public void onClick(View arg0) 
   {
      // TODO Auto-generated method stub
      WifiConfiguration wifi_configuration = null;
      wifi_manager.setWifiEnabled(false);

      try 
      {
         //USE REFLECTION TO GET METHOD "SetWifiAPEnabled"
         Method method=wifi_manager.getClass().getMethod("setWifiApEnabled", WifiConfiguration.class, boolean.class);
         method.invoke(wifi_manager, wifi_configuration, true);
      } 
      catch (NoSuchMethodException e) 
      {
         // TODO Auto-generated catch block
         e.printStackTrace();
      } 
      catch (IllegalArgumentException e) 
      {
         // TODO Auto-generated catch block
         e.printStackTrace();
      } 
      catch (IllegalAccessException e) 
      {
         // TODO Auto-generated catch block
         e.printStackTrace();
      } 
      catch (InvocationTargetException e) 
      {
         // TODO Auto-generated catch block
         e.printStackTrace();
      }
   }
});