If you're talking about launching an executable on demand, then you'll need a launcher, which is what kfmon and NickelMenu are. Otherwise, you'd need to code your own launcher program to monitor for and take in user input, but then what would be the point?
But if you mean launch automatically from device boot up, you'll probably need to do it through udev. You can read dstaley's write up on
Tailscale for hints.