How much power is generated from a typical solar-powered watch

So to confirm - you want a LiPo charger + a buck-boost regulator to 3.3V (primarily cause you want to be power efficient).

So you have a ton of options. If you want to go with the Microchip battery charger that comes with the Sparkfun breakouts (https://www.sparkfun.com/products/10217) or Adafruit breakouts (), there are a ton of buck-boost regulators you can put in the next stage. I personally use the TPS63031DSKT in one of my designs, and I'm using the exact same schematic as in the first page of the datasheet (http://www.ti.com/lit/ds/symlink/tps63031.pdf). The efficiency curve is great for the Iout range you are expecting.

However, if you are starting from scratch, I'd look for a PMIC that combines the two like the LTC3558 from Linear (http://www.linear.com/product/LTC3558). That will really help cut down on board space, and cost. Really great chip - all its missing is a battery gauge. I know that MAXIM makes similar PMICs but I can't find it right now.

The minimum requirement is a diode from the PV (solar) panel to the battery.
This will clamp the PV panel voltage to a diode drop above the battery voltage.
Panel output will be > Imp and < Isc. It will effectively be close to being a constant current source. This arrangement will give you about Vbat/Vmp of the panel maximum wattage or about 11/18 or or around 60%.

You can get much closer to full panel output wattage with a simple buck converter. This could be a discrete design using a few transistors and an inductor - but it's easier and almost as cheap tp use something like a MC34063. These are very old, lower max frequency than most modern SMPS IC's, but very flexible, available and low cost.
A MC34063 buck converter can be built with the IC, an inductor, a Schottky diode and a few resistors and capacitors. Efficiency can probably approach 90%. Using an external MOSFET will help efficiency.

You can get close to MPPT performance by using the panel loaded voltage as your controlled voltage - the converter functions to try and keep Vpanel at Vmp. This can get within a few percent of MPPT power out over much of the range of solar input.