Payment Gateways choices

Hi,

I am looking for clarification on the available payment gateways for Zoho Invoice. There used to be more than I see under the setup. So I am wondering:

Can you integrate Google Wallet?
Are there plans for Apple Pay integration?
Are the plans for Dwolla integration?
If none of the above, is there a custom option and a tutorial where we can set up these or other gateways?

Thanks,

Helen