We've already talked about how you can connect to many set-top boxes directly with apps, but these accessories give you flexibility in other areas, from getting Freeview signal anywhere to turning your iPhone into a universal remote to streaming and controlling any kind of set-top box.
PCTV Broadway 2T - £150
This Freeview tuner connects wirelessly to your home network, allowing your iPhone or iPad to connect to it and stream the channels it's receiving. You can even connect to it from anywhere over the internet, to get your home channels. It connects over Wi-Fi, so is flexible (though it still needs to be hooked up to your aerial by a cable), and can still act as a Freeview box for a TV, thanks to its twin tuners and video outputs.
equinux tizi+ - £150
This teeny, tiny Freeview tuner (it's smaller than an iPhone!) can be placed anywhere to pick up a Freeview signal, which it then sends to your iPhone or iPad over Wi-Fi. This means you can watch TV channels even if there's no internet connection available.
It has a rechargeable battery, so it can run completely cable-free, and has some built-in storage for recording shows, from which you can expand with a microSD card.
Jabra Solemate - £100
If you've set up your iPhone or iPad in a room to watch something, the built-in speakers might not be quite enough to make all the dialogue and music crisp and clear. A Bluetooth speaker is a great option, because it keeps things portable, but can provide plenty of volume. Once it's wirelessly paired with your device, the Jabra Solemate can be placed anywhere, thanks to its built-in battery. The quality's really impressive too, and it's a durable, small design.
SlingBox Pro-HD - £160
The SlingBox idea is simple: watch your home TV from anywhere, no matter what kind of set-top box you have. The SlingBox sits between your set-top box (say, a Sky box) and your TV, passing through the video so you can watch TV as normal. But it also takes that video and streams it over the internet, so with SlingPlayer's app on your iPhone or iPad you can watch anything you could at home (instead of a limited subset of channels, as with the Sky Go app), and control the set-top box from your device.
Griffin Beacon - £40
The Griffin Beacon is an infrared controller that sits near your TV and turns your iPhone into a universal remote. It's roughly the size of a cupcake, so there's no need to worry about it cluttering up your television set-up.
Basically, you use your iPhone to wirelessly control the Beacon, which then sends commands to your TV or settop box just like a normal remote control would. You can set it up simply with a huge range of devices using the built-in library of commands, or there's a learning feature for adding new controls.
Apple TV - £99
The Apple TV does a couple of great things on its own - it lets you watch TV shows from the iTunes Store or from Netflix for starters - but it's even better when you connect it to an iPhone or iPad. With AirPlay, you can send video from your iOS device to your Apple TV, so you can watch it on the big screen. This could be something from apps like iPlayer - however, take note that not all video playing apps support AirPlay - or something you've found on YouTube.
The idea of having a 'second screen' while watching TV has taken off hugely since the launch of the iPhone. The idea is that you can enhance what you're viewing with apps, whether you're playing a game along with it, looking up that actor you recognise but can't remember where from, or chatting with friends about what's happening.