Using the PowerShellToys PowerShellWebPart, I was able to insert a PowerShell command prompt inside my SharePoint page with only a few lines of code and some html. Here is the PowerShellWebPart template that I used:
To use this yourself, just install the PowerShellToys PowerShell Web Part, modify the web part, open its source editor and paste the above example in. Then just click "Apply" and voila!
Other PowerShellWebPart demos.