Stop, stand there where you are!

x86_64 machine code, 10 bytes

Hexdump of the code:

48 69 c9 ca fc 59 38 e2 fe c3

Source code (can be assembled by ml64 of Visual Studio):

    TITLE   heh

PUBLIC  mywait
_TEXT   SEGMENT
mywait  PROC
    imul rcx, 945421514
myloop:
    loop myloop
    ret
mywait  ENDP
_TEXT   ENDS
END

Performs an empty loop, starting from the specified value down to 0. I chose the multiplier 945421514 empirically by trial and error, until my test program output satisfactory results.

Test program (waits 10 times for each of the durations 1, 5 and 25 seconds):

#include <stdio.h>
#include <time.h>

extern "C" void mywait(int);

int main()
{
    int durations[] = {1, 5, 25};
    for (int duration: durations)
    {
        for (int i = 0; i < 10; ++i)
        {
            clock_t before = clock();
            mywait(duration);
            clock_t after = clock();
            printf("%f\n", (after - before) / (double)CLOCKS_PER_SEC);
        }
    }
    getchar(); // now take a screenshot
}

The result:

1.003000
1.000000
1.004000
1.006000
1.005000
0.998000
0.995000
1.000000
1.005000
1.004000
4.999000
5.003000
5.035000
5.010000
4.992000
5.003000
5.003000
5.019000
5.026000
4.989000
25.041000
24.993000
25.049000
24.988000
25.038000
24.948000
25.007000
25.014000
25.053000
25.021000

I ran this program on a Windows computer that has nothing else to do. If it runs some applications, the waiting times are more erratic.

The CPU speed is 3.9 GHz. It seems that this code is barely good enough for current PC technology - if the clock frequency is about 8.8 GHz, the multiplier will not fit into a signed 32-bit int.

---

P.S. As this answer doesn't check how much time has passed, it is a candidate for the bounty.

Bash, 29 25 24 23 19 bytes

w()(ping -t$1 1.2)

Accuracy test (time) where $1 = 1 second:

real    0m1.012s
user    0m0.001s
sys     0m0.002s

Thanks Dennis for shaving the byte count down to 19 from 23!

EDIT: I've changed the IP to avoid ping on Linux pinging 0.0.0.0, which is the loopback device.

---

How this works

ping has a default timeout of 1 second, so, when contacting an IP address which does not exist, ping can't continue until either the time out has passed, or it has got a reply from the IP.

-t tells ping to try $1 number of times on this fake IP address, forcing ping to take $1 seconds to complete the ping.

---

It's eligible for the bounty! No loop!

Matlab, 33 bytes

function f(t)
tic;while toc<t,end

Or you can also use this in Octave: try it online

Matlab, 31 bytes

As suggested by @flawr, it can be done with an anonymous function (it should be assigned a name in order to use it):

@(t)eval('tic;while toc<t,end')

Example:

>> f=@(t)eval('tic;while toc<t,end');
>> tic, f(2), toc
Elapsed time is 2.000323 seconds.