AFAIK it's not possible at this time using the public API. Maintenance windows are on the roadmap and should be available very soon. It believe enabling/disabling host monitoring using API will be included with release of maintenance windows.
Or if you have time & courage, you could try play with the private REST API (undocumented) - the one UI is using. It does not look that complicated, you just need to figure out how to send valid headers.