Lost in HERMS ... Flame Sensor / Ignitor

I've been beating my head against this for a while now, and this is the only missing piece of the puzzle.

I'm looking to make a propane based HERMs system using propane for the HLT exchange, but I'm coming up blank when it comes to having the controller turn on/off the flame. I understand the use of the solenoid valves to control the level of the flame, but once the flame goes out completely, how can I be sure the pilot is lit before the gas starts flowing?

I found this, http://bostonheatingsupply.com/sp10764c.aspx and it seems like it's the closest thing to what I'd want, but I'm not sure whether or not I could mount it properly for use on a Banjo burner. I'm open to either an open flame pilot or an electronic ignitor.

For obvious reasons, the open flame pilot concerns me due to a draft coming in and blowing it out. The electronic ignitors are known to misfire on occasion.

How are people doing this?

I own one of the valves with the separate high voltage spark ignitor, and one of the hot surface ignitor smart valves.
The hot surface is SO much nicer in every respect.

OneHoppyGuy has a good post here talking about it.

That valve plus the hot surface ignitor and a 24 VAC transformer are all you need.

Thanks for the reply. WOW! $130+ a pop for those are pricey, but I understand his logic of safety. That's ultimately what I want, and is safe and fault free firing system. All of these are for NG, but I'm looking for propane.

I just found this thread https://www.homebrewtalk.com/f51/gas-temperature-control-dummies-116632/ so I'm gonna read that for a bit, but I'm sure I'll be back.

If you get the valve in the link, it includes the parts required to convert the valve from NG to propane. It's just a little bit thicker spring and a different color cap. It'll take you 2 minutes to convert.

If you want to go HSI or DSI route then you just need a VR8245M valve (it does either HSI or DSI), 24vac power supply to power valve, and either a 780-504 DSI module or a RAM-H HSI module, and flame rod to sense ignition.