Poll: A new life to a "spoiled" / outdated smartphone

Not so long ago, I dropped my smartphone on a tiled floor, as a result, the glass with a touchscreen cracked. One crack, thin, does not interfere with the call, and all functions are working. But the eye is unpleasant. The smartphone itself is not expensive, Android OS, Chinese, purchased, this spring, it can be repaired by ordering a touchscreen (about $ 30). But soon it will still become obsolete, and therefore I do not see the point in the additional costs for it. I think to adapt it for other purposes. So I decided to conduct a survey, and find out your opinion on how to deal with a broken (but still alive) or outdated smartphone

The smartphone may simply be outdated or faulty. The types of faults can be different, the failure of any module, but so that the remaining functions remain working. Given that new models of smartphones are constantly emerging, with new features, this issue can affect many.
Immediately I would like to say that we are talking about the constant use of the smartphone in one capacity or another, i.e. Once set and configured.
With your permission, interesting suggestions in the comments will be added to the post itself. Such options as use as a flash drive, a card reader for micro SD cards, an audio player, etc. I consider not essential.

So, while I will describe several options

Using a smartphone as a 3G / 4G modem, plus a WiFi access point. In almost all devices, this function is already there, you do not need to install anything else. We connect the necessary tariff, we adjust safety, we turn on in the socket on constantly, we use.
Cons: Usually the mobile Internet is more expensive and slower than others. And I don’t know how it is with others, but it’s not very stable for me, the Internet disappears.

Using a smartphone as a surveillance camera. In this case, install the software and you can use it. Everything is quite convenient, WiFi connection, power from the nearest outlet. Here it is necessary to properly fix and possibly disguise (at least under a regular video camera). Use case: for example, monitoring the apartment when you are not at home, and a small child alone or with a nanny. You can still save all the videos on the device itself, then the network will not be needed.
Disadvantages: it is desirable to use indoors, in a zone of stable WiFi, if used outside or at an entrance can be stolen, cameras are poorly filmed at dusk, and there is no possibility of shooting in the dark, the devices are not adapted to the harsh weather conditions.
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Using a smartphone as a webcam to a computer. Just as in the previous version, you need to install the application, and you will have a wireless webcam. But with real need, it is much easier to buy a regular webcam. With one-time use, the current (new) smartphone will suffice.

Using a smartphone as a DVR and / or GPS navigator in a car / motorcycle. Everything is very simple here, we install the program you like and go ahead, in the case of the GPS navigator everything is already there, although it can be replaced. There are a lot of attachments for mounting, and power is no longer a problem. Both functions can be used simultaneously.
Cons: there are no special mounts and wires (you need to additionally buy or adapt), the need for manual on and off, long loading after a complete shutdown, in winter at low temperatures problems with the battery are possible, although with a constant supply of power is not a problem, but still.

Not yet considered the possibility of using a smartphone as a home server. If anyone tried to describe, I will be glad to read.
I added this post to the Mobile Development hub, although those who write for mobile OSs are likely to use them for tests in their projects. But maybe you have original ideas or ready-made solutions.

There will be more options if your smartphone has a USB-OTG, HDMI or other video output.

UPD Small subtotal
Unfortunately, the article turned out to be a bit holivaron, but there are still more interesting comments.
So from the vote it is clear that all the same it is worth trying to adapt it somewhere, well, or use it further as it is.
But according to the second survey, it turns out that you shouldn’t do anything with it. In general, I'm confused.

But the options for using a new smartphone are quite interesting.
From user seventh, I learned about a set of servers ;
I liked the idea of hermit931 about the projector. But honestly, I do not know where to get the old filmoscope. Although it may be strayed where on the Internet, but I have not yet searched. And I really liked the idea.
I was also interested in the option from PyroRed about the GSM-SIP gateway for a PBX, I’ll have to dig into this topic further.
There is a useful idea from constv to use as an alarm. By the way, programs for this kind already exist. And what, hitched to the front door and all. Sit at work, and you a letter: the door opened + photo.
As a controller for a copter ( Vilko ) is also good, and indeed for any toy.
If USB OTG were available, then server functions would be very useful, and it would be possible to download torrents. But not on my USB OTG. Yes, and many do not have it.
There were a lot of ideas for using a smartphone for home. Almost all of them can be collected into one, something like a single desktop device, display any information on the screen (for monitoring), or at least just a beautiful clock. And hang a bunch of tasks, incl. and smart home controller, etc., well, media player too.