Let's step back for a second. The 2400BT has iphone Pandora control through the cable, which means that you can control the Pandora app fully when an iphone is plugged in. When streaming Bluetooth, the 2400BT can't tell an iphone from a hole in the wall. It just receives audio streamed to it, and plays it through the speakers. So, using Bluetooth, there is no difference between using an iphone or an Android phone. When you're streaming Bluetooth with your Android phone, you can stream whatever the hell you want, from music to audio on a website; it makes no difference to the headunit.
The i-device that you would want is the iphone, or the ipad with 3G. The reason for this is that Pandora needs a constant internet connection, so it would be pointless to have an ipod with Pandora in your car, unless your phone can act as a wireless hotspot. So if that's the case, and you can set up a mobile wireless network, then yes, an ipod touch is what you're looking for. There are tons of 8GB on Craigslist for relatively cheap, or buy from the Apple refurb store.