There is one thing to consider with the sequential+brake modulator light like I have though.....it might be illegal.
I've had two deputies and one city officer here tell me that it's illegal...just like a modulating headlight is also illegal here. However....and that's a BIG however, everyone of them told me that there isn't an officer in this state that would pull me over for my lights alone. They all understand that you're trying to be seen and it's a safety issue. That said, if they saw you doing something stupid, or pulled you over for speeding or some other offense, that they might (depending on your attitude...everyone of them said that attitude is everything) give a ticket for the light. However, it's a non-moving violation and all you'd have to do is show them that it's been disconnected and the ticket would be voided.
You might wanna ask before you commit to buying one.

Why go through all that. The manufacturers who sell the modulators include a copy of the Federal Motor Vehicle Safety Standard that authorized the modulators. Carry a copy of it and show it to the officers. If they still give you a ticket, take the copy to the court clerk and asked for it to be dismissed.
Headlight Modulators:
TITLE 49--TRANSPORTATION
CHAPTER V--NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF
TRANSPORTATION
PART 571_FEDERAL MOTOR VEHICLE SAFETY STANDARDS--Table of Contents
Subpart B_Federal Motor Vehicle Safety Standards
Sec. 571.108 Standard No. 108; Lamps, reflective devices, and associated equipment.
S7.9.4 Motorcycle headlamp modulation system.
S7.9.4.1 A headlamp on a motorcycle may be wired to modulate either
the upper beam or the lower beam from its maximum intensity to a lesser
intensity, provided that:
(a) The rate of modulation shall be 240 <plus-minus<ls-thn-eq>40
cycles per minute.
(b) The headlamp shall be operated at maximum power for 50 to 70
percent of each cycle.
(c) The lowest intensity at any test point shall be not less than 17
percent of the maximum intensity measured at the same point.
(d) The modulator switch shall be wired in the power lead of the
beam filament being modulated and not in the ground side of the circuit.
(e) Means shall be provided so that both the lower beam and upper
beam remain operable in the event of a modulator failure.
(f) The system shall include a sensor mounted with the axis of its
sensing element perpendicular to a horizontal plane. Headlamp modulation
shall cease whenever the level of light emitted by a tungsten filament
light operating at 3000[deg] Kelvin is either less than 270 lux (25
foot-candles) of direct light for upward pointing sensors or less than
60 lux (5.6 foot-candles) of reflected light for downward pointing
sensors. The light is measured by a silicon cell type light meter that
is located at the sensor and pointing in the same direction as the
sensor. A Kodak Gray Card (Kodak R-27) is placed at ground level to
simulate the road surface in testing downward pointing sensors.
(g) When tested in accordance with the test profile shown in Figure
9, the voltage drop across the modulator when the lamp is on at all test
conditions for 12 volt systems and 6 volt systems shall not be greater
than .45 volt. The modulator shall meet all the provisions of the
standard after completion of the test profile shown in Figure 9.
(h) Means shall be provided so that both the lower and upper beam
function at design voltage when the headlamp control switch is in either
the lower or upper beam position when the modulator is off.
Here's the Federal Law that prohibits States, Counties and Municipalities from declaring equipment illegal that has been authorized by the US Department of Transportation
Title 49, United States Code
Chapter 301, Motor Vehicle Safety
Sec. 30103. Relationship to other laws
1. UNIFORMITY OF REGULATIONS The Secretary of Transportation may not prescribe a safety regulation related to a motor vehicle subject to subchapter II of chapter 105 of this title that differs from a motor vehicle safety standard prescribed under this chapter. However, the Secretary may prescribe, for a motor vehicle operated by a carrier subject to subchapter II of chapter 105, a safety regulation that imposes a higher standard of performance after manufacture than that required by an applicable standard in effect at the time of manufacture.
2. PREEMPTION
1. When a motor vehicle safety standard is in effect under this chapter, a State or a political subdivision of a State may prescribe or continue in effect a standard applicable to the same aspect of performance of a motor vehicle or motor vehicle equipment only if the standard is identical to the standard prescribed under this chapter. However, the United States Government, a State, or a political subdivision of a State may prescribe a standard for a motor vehicle or motor vehicle equipment obtained for its own use that imposes a higher performance requirement than that required by the otherwise applicable standard under this chapter.
Wasn't able to find anything on brake light modulators but you should be able to find something on your state's motor vehicle code online. From what I can find out California authorizes it and most states don't have any restriction against it.
Marty