Purchase a glass square at home depot for ~$4 for a 12" x 16" piece. You can get a smaller piece or larger piece depending on how big you want your screen to be and/or what size of a box you have handy. The length and height of your glass should be the same as the length of your box so that it can be slid in nicely at a 45 degree angle. The glass at home depot is used as replacement glass for picture frames and small projects, so look for glass around 3/32" to 1/8" thick.
Go to a local window tint or car tinting company and ask for a bout a 14" (inches) x 3' (ft) section of mirrored window tint @ 15% reflectiveness/visibility. Although this is ideal, the one I got looked way too mirrored but it worked great! This cost me $5. Don't waste your time or money buying the tint at home depot or online, you get way too much and it cost about six times as much.
Apply tint to glass. With patience you can do it, just use plenty of water, a squeegee, and give it a day to dry. Ideally, you can let the window tint guy just apply it to your glass.
Position box on it's longer side, with the opening facing forward. On the back of the box, find the center and cut a circle out just large enough for your camera lens. You can find the width of your camera lens by it's lens size (i.e. 67mm, 54mm, 50mm). This is usually the same as the filter you put on your lens. You can put a bit of duct tape across the hole on both sizes and then cut a cross and it will make a really good holder for your camera lens and reduces light coming from the back end.
Position mirror glass into box at a 45 degree upward angle. Make sure the film is on the outside. Take a peak through the back side to make sure you can see through it alright (it should be slightly darker but your camera will adjust for it). Now place your ipad on the bottom of the turned box so that it faces the mirror. It's reflection should now be in the center of the hole you made, if not, make some adjustments to the height or position of the ipad.
Download the free app called "Dv Prompter" for your ipad or iphone, or another free program for your computer. You can run text through this in a variety of cool ways and once you figure it all out, you can mirror text for reading on your homemade teleprompter at a speed and text size that is best for you.
Plug your camera through the back and hit record!