For iOS you'll need to sign it using the apple tools and such -- it is required to get it into the app store. Note that your client should be the one who signs up for the account and generates you the certificate.
I think Microsoft also requires one to use special certificates to sign code going into the windows marketplace.
Do you know that GlobalSign code signing is not the same as the code signing Apple requires of its developers? Apple's code signing is strict enough that you should not need GlobalSign or anything similar, IMO, especially if the code signing is in the business entity's name.