I'd say "all of the above".
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I'd suggest spelling out exactly what you are looking for, and posting about it in Developers to see if your 'bribe' could convince anyone to take up your cause or point you to a similar app/driver out there you could easily modify. I'd error on spelling out what you know (e.g. I would like to be able to trigger this exact API call, etc.)
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I'd also look at the sample apps and drivers out there to get a sense of what you could do.
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If your device has pretty straightforward Rest APIs and all you need to do is push commands to it, you could easily write an app, RM rule or even use the awesome Momentary HTTP Switch (instructions) to do this. For example, I use this to have Alexa Routines and some automations in Hubitat call rest APIs when the switch is pushed and includes a JSON payload for the command. Looking at the API, this might be your first starting point to get a sense of what you want to do with simple switches.
Lot's of options.
