When it comes to alarms for polyphasic sleepers I've heard of some really crazy things, my solution is much simpler so I'll describe that here.
The key with alarms is mostly about routine, lot of polyphasic sleep guides talk about doing things like practicing jumping out of bed when you hear your alarm, so it becomes a programmed response. To do this you would just lie in bed during the day and set the alarm for a minute in the future and then really spring out of bed quickly when it goes off... I've seen people say to do this like 20 times to train the response.
Then the method of the alarm itself comes into play. The craziest one I've heard of was someone who hid the keys to a locked box with the arlarm in it in bottles of water. So you'd have to go to the kitchen and empty the bottle to get the key and then use the key to unlock the box with the alarm. Crazy! :)
I actually have a much simpler solution for alarms. I need the alarm the most after the 3.5hr core, so when waking up between 12-1am, though it does really help in the morning and with midday naps too.. a good alarm system helps avoid naughty oversleeping which can really throw the routine.
I use an alarm (again, the wonderful Sleep as Android) that supports QR code scanning. So I have a QR code printed and stuck on the inside of the pantry in the kitchen. When my alarm goes off I have to head out to the kitchen and scan the QR code in the pantry. While I'm out there I often eat something and have grab a coffee. If I don't turn the alarm off, the Android Wear watch starts vibrating like crazy on my wrist and the alarm gets really loud and annoying.
Simple, but works really well. If you want to make a QR code like the one below, head over to QR Code Generator.
The other thing that helps with waking me up is the sleep as android integration with my hue lights. As the alarm goes off the light next to the bed starts slowly turning on, starting red and ending quite bright indeed. This can get the hormones in the right place to get you up and out of bed. I'm hoping to eventually replace the light with something like the NeuroOn mask that has LED's inside it that are timed to turn on with you alarm.
BTW if anyone from NeuroOn reads this, you know you want to send me a review unit ;)
So to summarize: