OK, so the "Flash" command in CoCoHue would do you what you want, but what that really does is set {"alert": "lselect"} on the bulb or group via the Hue API, which will make them fade up/down for about 30 seconds. Sending this command about every 30 seconds would keep the effect going indefinitely, I suppose, but it's all that Hue bulbs support natively. Beyond that, you could do like you do with any bulb and use a rule or custom app to send a series of repeated on()/off() or setLevel() commands to get the desired effect.
Speaking of custom apps, I'm aware of one but don't know if it supports HSM intrusions as a "trigger": [RELEASE] The Flasher - Flash your lights based on several triggers.
