Im familiar with blender, not sure why you mention it?

Just ignore him

truuuuuuu

Because you can use Blender to do vector work and gimp for raster. Blenders ability to draw in vectors is great in some ways too, because you may be designing your interface in 2d. But should you want the z axis, it's there. It comes in handy when you want something 3d to look 2d. Furthermore the curves and options for types of curves are very diverse in blender. Your curves have paths and can be followed easily. You can convert your curves to meshes for further shaping. The node layout of materials + the node layout of composting is superb and top of its game. I could go on, but the last couple comments by you two are retarded.

Well i can't seem to find any tutorials on how I would start creating something like this; https://www.assetstore.unity3d.com/en/#!/content/30892
Can anyone point me somewhere?

Draw the UI on paper you want.

Scan it

Trace it in whatever program (recommend illustrator since you'll be able to match any resolution : fantastic for UI)

Colour it in illustrator or in other colouring program.

Voilà !

is that the typical process?
yeah i'm not very fluent in illustrator, i assume they have tools to make a tracing more crisp/clean?

Yes. Especially the newer version (Illustrator CC)

I mean, you could do it without the drawing process. But honestly, a lot of people in the design industry are doing it because a 6-14 hour straight shift on the computer can give headaches... Drawing helps for that purpose and the only limit is your creativity.. so ... Yeah

Know any god tuts for illustrator?

I would suggest you to start with this :