I want to build my super cool auto flower water gadget. I'm looking for some arduino module like valve or water gate, which can be controlled by input power. So, it can open or close water flow from some bottle by a signal. Any ideas?
Do you need to control only the on/off flow of water? Do you need control over variable flow? What amount of flow and pressure are you talking about? As you can see, there are a lot of additional questions that would shape an answer.
From a bottle suggests fairly low flow and pressure. I am not really familiar with something that size (maybe a drip irrigation system valve); but I have controlled solenoids before with power transistors and/or relays. Solenoids such as what you'd find on a Rainbird irrigation valve. These are often 24VAC and pull somewhere from 125 to 250 mA (depending on model). (I've also used these successfully with small air cannons like for confetti throwers.)
If you connect the valve with some PVC pipe to your bottle you should be able to control the on/off state easily. If you need the ability to control the flow in a variable way, you will probably need to look for some kind of a stepper-motor or servo controlled valve.
Due to the date of post this is more for others who come across this question in search of a solution for a similar project.
Most sprinkler related valves require a high pressure system similar to what your city water supply has (~60-90 PSI). To open the valve requires both a "high" pressure source of water and the solenoid to be activated. If you are connecting to a garden hose this is fine. If not this is no easy feat. I used a 390 GPM pump and couldn't open the valve.
If you are connected to a 2L bottle or rain barrel you'll need something designed for low pressure. Look for a gravity fed solenoid valve instead. Here the maximum pressure is around 7ft of head with water (or 3 PSI) and there is typically no minimum pressure. I ended up using one from valves4projects (suggested by earlier answer) and was happy with the results.