I would recommend choosing any teddy bear you would like to have, and then select a sound device with sleep-sensor and non-stop system (tick of extra features on the product page).
Here comes the explanation :)
There are 2 types of sound devices that you can choose from, one has sleep sensor and non-stop system, while the other does not have these additional features.
The first sound device is a standard mechanism that plays white noise for 1 hour. This mechanism is good to use if the child only has trouble falling asleep when the child is going to sleep.
The second sound device is also good for children who are having trouble falling asleep. But it is also good to have for when the child wakes up a lot (eg at night). There are 2 modes that you can choose from: sleep mode and non-stop mode.
About Sleep Mode
When the audio device is set to sleep mode (sleep sensor is used), the audio device plays white noise for 1 hour before the sound gradually disappear and goes into an idle mode. If noise or other kinds of sounds occurring around the audio device (which is in idle mode) the audio device will reactivate and play white noise, before it turns itself off after a few minutes. And so it will hold on: the noise around the teddy bear appears and the audio device is reactivated and then turn off after a few minutes.
About Non-Stop Mode
The second mode that the audio device has is non-stop mode. This mode allows the audio device to play white noise for 12 hours.