Controlling hot tub thermostat remotely

I have a Hot Spring brand hot tub in a second (weekend) home that's about 2 hours away.  I would like to be able to control the temperature remotely, so I can start it heating up when I'm on my way to the weekend house.
 
Any suggestions for how to handle this without totally hacking apart the tub?  The temperature is currently controlled with temp up/temp down buttons on a keypad on the tub.  It has no remote capability built in.
 
Edit: It looks like Hot Spring does offer a remote monitoring solution, but I assume it is either (1) only sold with new tubs (mine is a couple years old) or is (2) ridiculously expensive.  See http://www.hotspring.com/hot-tub-accessories/connextion

You could control the electricity using a contactor or similar, assuming you want to minimize how often it runs and heats. From a quick look, it seems like you should be able to put a controllable contactor between the control terminals and heater element.
 
I would investigate their OEM option first.

You would have to hack into the wiring to do so. If you control the input source the pump may be injured, water stagnate, or the inductive load corrupt your controlling switch without the proper contactor/motor starter.
 
I would seriously lean toward the manufacturer designed solution first.

I've been wanting to do this on my (ancient ;-) hot tub for a while. Because it is ancient, it just has a regular bi-metal type thermostat, which is a trial and error affair to get set to the correct point- a pita for lowering the temp for a few days.

Two operating modes-

1 Normal- runs based on a timer. This is how I currently do it- heater runs to setpoint (around 100 degrees), twice a day, about 1 hour each time, set to just before we typically use it.

2 Demand- runs any time the temperature drops below the thermostat trip.

What I had in mind was to use the Demand mode as my low temp failsafe- set it for 50 degrees or something to prevent freezes. Then add a separate temperature sensor to monitor the tub, and an automation controlled relay contact in parallel with the exiting thermostat. That way I am protected from any automation failures, and I can control the temp from my automation system. I think it would be a pretty simple mod to the existing control box...

Thanks for the replies.  If anyone else has any ideas, feel free to chime in.  I'll definitely explore the OEM option and see if it's possible to add.
 
I dug around some more and someone on another forum had an interesting (and simple) solution.  Assuming the temperature sensor used by the tub is just a basic thermistor, you could wire in a relay connected to a second resistor (or potentiometer).  When you engage the relay, the added resistance from the second resistor/pot will make the tub think it is warmer than it actually is.  So, for example, I could calculate (or determine by trial and error) the resistor size I need to make the tub think it is 100 degrees when it is actually only 80.  Then I would just engage the relay when I'm not there and the tub will only keep the water heated to 80 degrees.  When I want the tub to heat up to 100, I can simply disengage the relay (using whatever remote relay control I want) and the tub will suddenly think the temperature is only 80 and heat up again.
 
My only concern is the possibility that some weird safety mechanism may kick in on the tub when I engage the relay and the water is already 100 degrees -- the tub will suddenly think the water is 120 degrees.  Does anyone see any reason why this would damage anything or throw the tub out of wack?

Not familiar with hot tubs too much but your idea sound bullet proof to me.  Your parallel resistor would be calculated and tested to fool the stat into thinking it is 100 degrees and the sensing system would take it to 100 degrees (it thinks) or whatever setting you like. there would be no overheating to kick some protection in.
 
This would be just like having a badly calibrated sensor. Nobody is going to know, or care.
 
Having said all that if a two stage heater is in effect another sensor could think you need the full heater on instead of tweaking the temp with the smaller element. No harm done I wouldn't think and what are the chances of each stage having it's own sensor?

Controlling hot tub equipment with smart phone
I bought the smart pool timer from Thermomart in the following link,
http://www.thermomart.com/cellphone-wifi-app-google-alexa/Timer-Pool-Spa-Hot-Tub-Sauna
The product works. It’s good quality. It is easy to download the app and I paired it in 15 minutes.
This timer saves me $30-$50 a month and also I do everything on my cellphone or by voice (by Amazon Alexa, Google Assistant) from anywhere!
The Timer can be programmed as scheduled (24 hours 7 days with 8 events) or loop timers if you want to use more event every day. It has a countdown timer too.
It has a waterproof box and it is suitable for outside. I use the sharing system and now my wife can control the pool pump too.
Would definitely recommend purchasing.

If the thermostat is set and heating/running, and you remove power, then restore power (for instance via the circuit breaker), does it start running again when power is restored?
 
Or does it go in a standby mode and require manual activation to start running again.
 
If it starts running again, you should be able to use a standard smart switch to control a properly rated relay/contactor to switch the power.

That's essentially how I remote control my water heater.