On the Genesis forum, it was mentioned that a few people have MyKey. they are very happy with it.

Before you can get them to pay, you will need more evidence than "the mechanic said it caused the problem". Have they asked to see the unit to examine it for defects? Do you have evidence it was installed properly?
Good luck, but you may have to involve a lawyer or small claims court with some evidence.

Here is one comment from the Genesis forum
I use the MyKey Premium remote starter and have been very happy with it. It installs in under 1/2 hour with no tools needed and uses your OEM fob for control. The product also includes a proximity lock/unlock function which is very nice.

 

My evidence is, that the vehicle was working perfectly up until the moment the MyKey Premium starter was connected, then immediately after the wipers, headlights and HVAC ceased to function. I suppose it could a coincidence that at that exact moment something else caused the shortage. I'm sure if this happened to your car, you would feel the same way I do, that the started was defective and shorted out the system. The other supporting evidence is the Hyundai dealership had worked on the vehicle for a 5-month period. In fact, they worked with the Hyundai engineers in California to resolve this issue due to its complexity. It was his expert opinion, after extensive testing and diagnostics, that the remote started caused the problem, as common sense would dictate. I have been working with MyKey Premium company since the day it happened and over the 5 months we have exchanged 20-30 emails and letters trying to work out a solution, but the company has been uncooperative. I filed a complaint with the New York State Consumer Protection Agency. If this isn't resolved, I will be filing in small claims court. As far as sending the device to MyKey to examine the unit, I was advised not to send it to them because it was a key piece of evidence to support my claim, they could simply discard it... case closed. I also have concerns about MyKey Premium investigating itself, as this raises potential conflicts of interest and does not guarantee an impartial assessment. In fact, it is highly unlikely they will test the device and report back to that it was their fault and reimburse me the $1,800 in repairs. I would be naive to think otherwise.

 

I understand "it was perfect until I installed MyKey"

Unfortunately, your evidence to date is hearsay. Can you prove you did not cause it during the install?

You have what may be the perfect evidence in you hand. Until that is examined, you just have opinions. Perhaps you can get them to agree to have a third party examine it. I image it can be verified with some electrical test equipment.

I'm not a lawyer, certainly not a Judge, but until you show hard evidence, IMO, you have nothing. Get that unit tested, show it is defective, then you get $1800+cost. MyKey should be able to provide the value for testing.

 

A couple years ago, i had issues with the remote starter not working and I had issues with their "customer service".

What part did hyundai replace that they claim was affected by remote start?