From an Avalon to a Yaris, connecting you iPod to your Toyota can be very tough. There are a multitude of options that can just be overwhelming. The three main types of iPod adapters for Toyotas are wireless FM transmitters, direct audio inputs, and wired FM modulators.
Wireless FM transmitters are the simplest type of Toyota iPod adapter. These devices usually plug into your cigarette lighter. Once you plug in your iPod, the adapter will transmit the audio using a wireless FM signal to your factory Toyota stereo. Also, if you get an iPod specific FM transmitter, it will charge your iPod. So, like most people you are thinking easy enough, I'll just buy one of these transmitters, plug it into my cigarette lighter, and my problem is solved. In most cases, it's not that easy. Most people find FM transmitters pretty horrible. No matter what, you will have some sort of static in the background. Plus, the audio will drift in and out according to how powerful the radio stations are transmitting in you area. After about a month of owning one you will probably search for a better type of iPod adapter.
If you are lucky enough to have a Toyota that has the provisions for it, a direct audio input is your best option. A direct audio input uses the CD changer port on the back of the Toyota radio. This port along with the adapter allows for the best sound quality possible. Luckily, most Toyotas from 1998 to the present have this port. The better adapters will plug into the bottom of your iPod which will allow you to charge your iPod and will also allow your factory Toyota radio to control the iPod. This adapter allows you to fully integrate your iPod to your factory Toyota sound system.
So, What happens if your Toyota does not have the provisions for a direct audio input? Well, your best option will be a wired FM modulator. A wired FM modulator is similar to a wireless FM transmitter, but better. A wired FM modulator interrupts your Toyota's factory antenna cable and sends the iPod audio directly to the FM tuner through the radio's antenna port. Since the FM modulator interrupts the antenna, unlike a FM transmitter, no matter how powerful the nearby radio stations are transmitting your iPod audio will not drift or have static. This adapter is universal and will work on any stereo. The one downfall this adapter has is degraded sound quality. since the FM tuner's sound quality is not as high as a CD, you will lose a little bit of your iPod's sound quality.
Connecting an iPod to a Toyota can be a little difficult and confusing. Just remember that your best bet is a direct audio input. If your Toyota radio does not have the provisions for a direct audio input, the next best thing is a wired FM modulator. As a last resort, you can use a wireless FM transmitter, but I do not recommend it.