So just as an FYI and technical side-light:
JRemote and Gizmo require a wi-fi connection between the JRiver instance being controlled (in this case the Id) and the phone/tablet doing the controlling, but you do not necessarily need an external wi-fi router or an internet connection to get that working depending on your hardware. Full disclosure, I don't own an Id, but I have used JRiver on a headless raspberry pi in places where there was no wi-fi or internet access using the two methods described below. I should also clarify that I did this using an android phone not an iphone, so there may be some differences. The first method below should work out of the box with the Id, the other would require a change on JRiver's end.
Two alternatives, the easy one first:
1) If your phone has a "mobile hotspot" or tethering functionality you're golden. Most modern phones have the option (assuming your carrier permits). It effectively turns your phone into a wi-fi router. On my Samsung Note, the SSID and password are the same each time. So I configure my headless MC box to auto-connect to the wireless network that my phone provides when "hotspot" is turned on. When I want to control my headless MC box where there's no wi-fi, I just turn on my phone's hotspot, my JRiver box auto connects and JRemote and Gizmo work perfectly. The one bit of fiddling is that if you use your Id on lots of different wi-fi networks, your access key may not work correctly just at first, so you might need to specify the IP address of the Id/JRiver box in JRemote, but on my phone at least it shows you the IP of the connected devices on the same page where you activate the hotspot and its the same every time, so it was a one and done. This should work out of the box with the Id unless there's something I don't know about the Id handles wireless networks.
2) This one would require some tinkering on JRiver's side, but in the same way that most phones can be a mobile hotspot/access point, many commercial wi-fi chips can also act as an access point/router instead of a receiver. Richard mentioned this above in reference to a normal PC, but a surprising number of chips support both and with modern cards it works fairly well. Assuming the wi-fi chip in the Id supports it, JRiver could potentially code a switch or configuration option that would put the wi-fi card in the Id into access point mode. Then any device with a wi-fi receiver (i.e. your phone) could connect to the Id as though it were a router, and JRemote and Gizmo would work. To be clear, this isn't entirely theoretical, I did this with a headless raspberry Pi in my office for 6 months or so. I turned it's usb wi-fi card into an access point, and then when I came into the office my phone was configured to automatically connect to the wi-fi, and JRemote and Gizmo worked a treat from there. The linux network scripting involved is non-trivial for an end-user, so I wouldn't advise anyone to try and hack their Id into doing it, but it is potentially an option for more advanced users, and it's something for the devs to mull.
I used both methods daily for approximately 6 months each, and both worked great with my little headless MC box. Hope this adds to the discussion.
Last, but not least, if there's anything you need to do that you can't do in JRemote or Gizmo, I understand that the Id now supports remote access, so you could also use your phone to remote in and fix any issues.