People are turning to audio and visuals when it comes to technical subjects. However, you should consider doing an ebook first and turning it into an audiobook through a resource like Audible's ACX platform. You can hire a producer either through a royalty share program, so you don't have to shell out upfront cash, or you can do a pay-per-hour hire as well.
If you’ve got a way with words and expertise in a niche, there are plenty of sites that will pay for articles and content you write. Think of the sites you read regularly. What can you contribute to them that would be interesting? Research your niche and then look for ways to pitch articles. Many sites will simply have a submission or contact link in the footer. To get started, check out my full guide to becoming a freelance writer on the side and then submit your articles to places like Listverse, TopTenz, A List Apart, International Living, FundsforWriters, and Textbroker.
If you want to help shape products in their early stages, joining an online focus group or answering survey questions is a great way to make extra money online. They don’t pay as much as some of the other options we’ve highlighted, but you can join groups on sites like Survey Junkie, Swagbucks, and IPSOS that pay out through Amazon gift cards, check, or PayPal. You’ll be asked to provide a bit of information about your demographics (age, location, etc…), but after that you can get going making money through surveys.
If you have pop-ups and optins on every page, I would have to think that it would be a lot harder to convince someone to link to it. Especially since the pages where you have your optins (and probably receive the most traffic) are probably the same pages that you have your best content on as well that you'd be hoping to pitch in your outreach campaign.