My BMW 318ti compact has the original BMW Navigation Business radio/tape player. For looks and value, I wanted to retain this system instead of getting a new radio, but I also wanted the possibility to listen to podcasts from my phone (I always listen to X-Wing podcasts when traveling alone), maybe listen to music from a USB stick, and possible make phone calls hands-free. The simplest and cheapest way to do this is using an FM transmitter with Bluetooth capability (aux inputs can be added on newer systems, but not on my 2002-vintage radio). I have however read that the sound quality can be poor, that the microphone is in an inconvenient spot (too low), and the space around the 12V plug/cigarette lighter is quite cramped.
The alternative is a Dension Gateway. This is a small box that connect to the radio/navigation system and pretends to be a CD changer, hence the radio can talk to it. There are several versions available. Since I wanted wireless Bluetooth connectivity, I decided that the Gateway Lite BT would be the right one for me. It also comes with an USB port and you can get accessory cables with 3,5mm plug or iPhone/iPod connector. I worried about the difficulty of installation after reading some negative comments on Amazon, but then saw this (German) video with step-by-step explanation of what is a 30-minute job:
It took me about twice that since getting the cables arranged in a wat that would make the radio fit back in was quite difficult. I ended up removing the vents so I could access the cables from above. My radio already had a CD changer plug attached (I guess the CD changer slot in the rear, above the navigation computer is pre-wired) as well as a gray plug for the navigation system. I attached the gray navigation plug and the black plug that comes with the Gateway to the new radio plug, and everything works. I did not install the microphone for hands-free calling as I want to keep the interior looking original.
I can now switch to the Gateway by pressing the mode button (which cycles between radio, tape and CD) to switch to CD. With a USB stick connected, you get music playback from the USB stick – buttons 1 to 4 directly access the first to forth folder (alphabetically) on the stick, while pressing 5 lets you play music in all folders. It’s probably best to limit the amount of music on the USB drive for ease of navigation and to keep the time for indexing the drive down (you can do indexing on your PC with this software. The buttons for next/previous track on radio and steering wheel work. Unfortunately, there is no way to quickly change from USB to Bluetooth. If you want to stream audio via Bluetooth, you need to disconnect the USB drive first. On the Navigation Business radio, there also is no text display of the songs being played.
Even with these shortcomings, I’m satisfied. The most important functionality for me was the possibility to stream audio from my phone, which works fine. Listening to music from a USB drive also works fine if the collection isn’t too large and switching between USB and Bluetooth isn’t required. I cannot say much about the hands-free calling functionality since I didn’t install the microphone. I don’t think I’ll miss it even though I use it on my other car, as I have to admit that phone calls while driving are very distracting and should be kept to a minimum. I might try to get the built-in phone to work with a cheap pre-paid SIM card and redirecting incoming phone calls onto it from my iPhone. It certainly is a much nicer solution, both functionally and aesthetically, than an FM transmitter.
Other functionality that I haven’t tried is the optional AUX cable (which is suitable e.g. for MP3 players) or the optional iPhone/iPod connector that also allows control of these devices from the radio/steering wheel and text display (though not on my radio).