Probably not GET in these cases, as GET is required to be safe
the client does not request, and does not expect, any state change on the origin server as a result of applying a safe method to a target resource. Likewise, reasonable use of a safe method is not expected to cause any harm, loss of property, or unusual burden on the origin server.
How do you feel about spiders calling your lifecycle start point? or user agents proactively fetching your lifecycle start point just in case it is needed?
I'm not changing the state of the server in anyway
It's less about changing the state of the server than it is about changing the state of the resource.
- start a device
- stop a device
So these are pretty straight forward; think about how you would do it with a web site? There would probably be some status page for the device, with a hyper link on it saying "To start the device, submit this form". You would follow the link to the form, and it would describe all of the data required to start the device, and you fill out the form and submit it, and TADA, side effects on the device.
REST API's work exactly the same way: you read a representation of a resource, that links to a representation of a different resource describing how you can change the first one. You submit the second document, and behind the scene's the API does the necessary to change the first one.
REST API's are just giant bureaucracies: everything gets done by submitting forms. Need to provide some new service? that's a new form.