As the others have said, the only true untethered coldboot option is to install a modchip that automatically pushes an RCM payload.
That being said, there are ways to simplify pushing an RCM payload without a modchip. If you have an Android device (or a jailbroken iPhone), you can use that and the proper cord to push an RCM payload away from your computer. You could also purchase a cheap dongle that pushes an RCM payload, such as the NS-Atmosphere.
Edit: If you keep your Switch in sleep mode when you're not using it, and you don't let it die, then you're unlikely to ever need to push an RCM payload away from home. I have AutoRCM installed, and I've never needed my computer/Android away from home.