Yes, I've seen free to use web based services like this on Product Hunt. I've also seen many "products" on Product Hunt that are services that support/are supp

Yes, I've seen free to use web based services like this on Product Hunt. I've also seen many "products" on Product Hunt that are services that support/are supported by other services, like Whatsapp for the browser and 3rd party social networking tools, both of these types have even been in the top 10 for the day that are shown in the email newsletter. I'm not familiar with the submission process, but have heard it helps if you're connected there already. But if your product is big/cool enough, other people will submit it, for instance a new car from Tesla or product from Apple are usually shown on Product Hunt. Good luck!