What type of knock detection to you use on your other vehicles? You can make some DIY knock detection for tuning for fairly cheap. Search for "knock ears" or "detonation cans".
I like having a visual warning of some sort since I often have my stereo blaring. Even if detonation got bad enough to hear, I wouldn[t hear it over the stereo. I used a TurboXS knock light for years but it was very basic and I never felt that I could trust it.
So when it died a while back, I purchased a knock warning gauge off of eBay called the "Lil Knock Meter": http://www.ebay.com/itm/Knock-sensor-ga ... 35?vxp=mtr
. Here's their website: http://www.insaneimportperformance.com/
. It's actually a fairly cool little device that looks to have lots of potential when setup correctly. There is configuration software for it that allows you to change sensitivity, noise threshold, time, etc. It has both digital and analog out signals to use for logging the knock level. I've played with the settings and you really can tune the thing a lot more than anything I've seen from any other companies, and it's fairly inexpensive.
It also has an audio output so you can plug headphones directly into it. However, I wasn't happy with the sound quality and volume I was getting out of it so I also have a Y-splitter that I run into a cheap personal sound amplifier. I can then split this signal using a Y-cable and either listen via headphones while simultaneously recording the sound via my laptop. OR... I have a standard headphone input jack on the front of my Kenwood head unit that allows me to play the engine noise through my car stereo. With the windows up and the stereo cranked up, this is a great way to allow both the driver and the tuner/passenger to listen for knock in real time.