HDMI-CEC is a wonderful thing when you have it! It enables your TV to relay control signals over the HDMI cable which gives you the ability to control your Kodi mediaplayer, or similar device, with your TV remote. Unfortunately not all TV's support this and that leaves you with a few options with disadvantages.
The smart phone apps available for controlling Kodi are good, no question about it. But every time I put on my TV I need to find my smartphone or tablet and make sure I'm on the correct wifi. Call me old fashioned but I like the TV as a semi stand alone device if you know what I mean.
Secondary remotes come in a number of different types. There are the regular IR based once that require additional hardware, if you don't have IR reception on your device. Since all my Kodi boxes are Raspberry Pi based I need additional hardware. There is also stand alone remotes connected to wifi ro Bluetooth which are pretty good but expensive. As soon as your dog, child or other semi destructive member of your household get their hands on it will be broken or gone.
As I mentioned before you need additional hardware on the Raspberry Pi to support a remote control unless it's communicating over the HDMI port. I also want a cheap solution that I can easily replace if damaged or lost. And if possible I don't want a second remote control for my TV setup. Here comes Flirc and saves the day!
Flirc is a programmable USB IR-receiver that can be used with any remote control! It even has a profile for Kodi in it's setup application. It's usually recommended for Kodi users in combination with a standard Apple TV remote. Even if I like the Apple TV remote it's still a second remote. There are a number of unused buttons on any TV remote that can be programmed into the Flirc. In my case I realized that the up, down, right and left keys on my TV remote, that are crucial for Kodi operations, where unused while not in the menu system of my TV. If I tried to use them without the menu open there where no response from the TV at all.
The setup of the Flirc is really easy! Just connect it to your computer and download the software, select the profile and then program the buttons you want. Then just unplug it and connect it to your Kodi box. It is also very sensitive for IR-signals, all my Raspberry Pi's are strapped to the back of my TV furniture but thanks to my white walls the IR-signal bounces in there and are picked up without any problem.
It's currently priced under $23 on Amazon and really worth it. It can be used with any remote and you can replace your TV set and just reprogram it if needed.