You should be extremely specific about what you mean by "integrated" -- the term has no inherent meaning when you're talking about two platforms with expansive, but not overlapping, feature sets.
From a cursory look at the ShowPad API (which is more of an admin API) it's clear there's no built-in integration between their email tracking features, for example, and any outside platform. But since they also allow you to build and upload packaged HTML/JS web apps ​as a content type, one can't say you can't integrate web-side Marketo features like Munchkin -- as you could with any web app.
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