PowerShell Web Access is like webmail, but for PowerShell cmdlets. You log into a webpage that presents a Web-based console where you can run cmdlets, perform operations, and do simple remote administration tasks right over the Internet. There's no need for PowerShell, extensions, or cmdlets to be installed on the machine you are browsing with.
This means that yes, you can run PowerShell operations from your iPad if you have this feature enabled.
Best of all, it is free with a Windows Server license and is built right in. I do not see this in use a lot, but I think it is very handy. As the saying goes, "You might not need this until you need it, but when you do end up needing it, you need it very badly."
Be careful, though, as opening this facility up to users outside your network is just an invitation for security problems. Restrict access to the PowerShell Web Access site in IIS to only IP addresses local to your corporate network. Or even better, restrict that access to a few workstations on your local network and perhaps a static VPN address you can use to perform administration tasks remotely.
This free Windows feature is installed through Control Panel / Add and Remove Windows Features. You can also check out Microsoft's help page on this.