I wouldn't drywall over the window. Take a look at the options for recycled brick, they may match better than you think.

Beautiful clean modern kitchen! You have a great opportunity to put your personal stamp on the space with a unique backsplash. As you've heard already there are some different approaches. I'd probably place the backsplash up to the wall cabinets and up to the base of the hood. Then continue the backsplash at the same height (18"?) behind the sink. Then place an inspiring colorful picture above the sink to break up the wall. Here's a picture with pendants that aren't too obtrusive. Having multiple levels of lighting at different lumens makes a more inviting feel to the space. I couldn't decipher your flooring, but you may also want to consider adding some nature elements like a type of wood flooring, wood stools, etc. Good luck! If you need software to plan out materials check out our Home Designer software: http://www.homedesignersoftware.com/

When you're doing lighting in a kitchen it's a good idea to have good directed light over the main tasks areas, cooking, dishwashing, food prep. You could achieve this with downlights directed at those areas, or track lighting where you can direct/angle each of the lights on the track. Re the pendant over sink area, would need to be at a height that ensures safety - water & electricity, not a good combo. There may be some NZ standards that you can refer to, to get the correct info.

I'm not sure how easy/cheap professional systems are to install. But it might be easier to look at the IFTTT app which works with "smart things" by samsung and many other samsung products, belkins we-mo, and even fit bit.