"Monitorize" an Image
Matlab 2013, 150 bytes

Here is my attempt in Matlab. Definitely won't be the shortest code, but it's a start.

Warning, this overwrites the original image, so make a copy first.

Golfed Version

function  mi(f,n)
o=imread(f);
s=size(o);
imwrite([imresize(o(:,1:((s(2)-n)/2),:),[s(1),s(2)/2]) imresize(o(:,((s(2)+n)/2):end,:),[s(1),s(2)/2])], f);
end




Ungolfed Code, with improvements for odd image sizes and odd number of columns

function  monitorizeImage( filename, num_columns )

orig = imread(filename);
orig_size = size(orig);

f = factor(orig_size(2));
origsize_iseven = f(1)==2;

f = factor(num_columns);
num_columns_iseven = f(1)==2;

odd_even_size_mismatch = xor(origsize_iseven,num_columns_iseven);

img_resized = imresize(orig,[orig_size(1) orig_size(2)+odd_even_size_mismatch]);

leftimg = img_resized(:,1:((orig_size(2)+odd_even_size_mismatch-num_columns)/2),:);
leftimg = imresize(leftimg,[orig_size(1),floor(orig_size(2)/2)]);
rightimg = img_resized(:,((orig_size(2)-odd_even_size_mismatch+num_columns)/2):end,:);
rightimg = imresize(rightimg,[orig_size(1),floor(orig_size(2)/2)]);

monitorized_image = [leftimg rightimg];
monitorized_image = imresize(monitorized_image,[orig_size(1),orig_size(2)+ ~origsize_iseven]);

[~, ~, ext] = fileparts(filename); 

imwrite(monitorized_image,strcat(filename(1:end-length(ext)),'_',num2str(num_columns),ext));

end