I bought some of these units to help control the endless TV watching in our household. Although it has been less than a week, I would say that the time machine has had a dramatic effect on "screen-time" in our family.
Pros:
Kids love to earn the coins. Although the novelty will wear off, I am having no problem getting kids to do simple chores in return for a 30-minute time tolken. In fact, I'm having to think hard to come up with things. As they have more and more tolkens built up, I tend to make the chores take a bit longer, or require them to read, go outside, etc. They also love spending the coins. The kids do collaborate and barter on who is going to use their coin. I don't see this as a downside because I am more interested in them contributing to helping with household chores than I am in total tv time.
The coins are nice and solid. Good feel to them!
I am not involved in the usage and timing. They put the coin in when they want, and the time runs out when it runs out. I stay out of it.
Some things to think about:
When you read about the device, it states that it can support two devices per unit. This is technically accurate. However, one of the devices has to be coax, and the other has to be RCA. There is one coax input, and one coax output. There is also one RCA input, and one output. The # of coax devices these days is pretty small. You can convert RCA to coax with an additional unit, but that involves more wires and cost.
Once you put a coin in the machine, there is no way to cancel the remaining time, or use the menu in any way. The menu functions are setting the time, changing the pin, setting the clock, and manually unlock/locking the unit without a coin. Not a huge deal, just know that once the coin goes in, the unit is in run mode until the 30 minutes passes. If somebody sticks 10 coins in, the until will be tied up for 5 hours.
If you unplug the unit, is loses all the settings. No battery backup. Somehow our dog always seems to lay on the powerstrip.
The until does not support HD connections. So for an x-box 360, you may be degrading your signal quality.
Componet Video, Y-Pb-Pr, video signals do work. However, you cannot plug in the sound. So you will plug in your 3 video cables, and then output the 3 video signals to your tv. You will have to run the sound directly from the source to the back of the tv, so the unit will only interrupt the signal, not the sound.
Hard to ground one child from the TV. You can just take all their coins, however, if they have a coin they can activate the until. Yes, this unit DOES still require parental involvement at some level. Some people are surprised by this. Wake up people..
Technically you cold probably pry the unit open, but again parents can make the concequences clear if people are trying to cheat the system.
Older kids may just plug a new RCA cable into the device and into the TV. Be sure you don't leave extra laying around. Again, you still have to be a parent. For x-boxes and such, it is not as big of a deal since one end of the cable tends to be proprietary.
If you have a lot of children, be sure you think about how they are going to keep track of their own coins, and be sure you know how you are going to store the extras. You could probably put a bit of color on each coin so that kids have their own coin color and you know if they are using their own and not one from a coin misplaced by a sibling.
If you have a lot of devices, and they are all RCA, you are limited to one time machine per device. However, you can purchase a connection switch that allows you to plug 4 inputs into it, and then have one output leaving it and running into the back of the time machine. Remember that this may make it easier for older kids to just unplug connections and move them around (See still must be an involved parent comments above).
Overall I am satisfied with the device. It has minimized the amount of work I must do policing TV, my house is a bit cleaner, and the kids are adapting well to the system. I would recommend this system to busy parents that want a bit more control.