SDK security testing?

[TonyLovesDevOps]

This is off topic but I couldn't find a different contact method for y'all...

Have you all worked with any mobile security testing companies to harden your mobile SDKs, that you'd recommend (or possibly even more importantly, would not recommend)?

Background: I am trying to find a third-party mobile security testing company to test and help harden some iOS/Android SDKs that I help produce. The goal is to assure our customers that they are not integrating malware/vulnerabilities into their mobile apps when they integrate our SDKs. Sadly, the mobile security testing space seems to be full of charlatans who are primarily good at taking money and producing boilerplate security reports based on free testing tools. I'm hoping I can learn from the experience of others and find someone who does good work and can help us achieve this.