The New Year is a good occasion to re-evaluate your portfolio and start hunting for promising new investments. So we asked three top Motley Fool analysts which stocks they would be watching this year, and they turned up an IPO, the maker of an exciting new product, and a company that stands to benefit from a transformational shift in an established industry. Read on to learn why our contributors think these investment ideas should be on your radar in 2015.

Patrick Morris
One thing I will keep a close eye on in 2015 is how the spinoff of PayPal from eBay (NASDAQ:EBAY) progresses.

The press release announcing the move at the end of September included the following information:

PayPal is a rapidly growing global leader in digital payments and the most trusted digital wallet, with more than 152 million active registered accounts. Accounts grew 15% year-over-year last quarter. Revenue over the last 12 months grew by 19% over the prior year period to approximately $7.2 billion.

PayPal facilitates one in every six dollars spent online today. Total payments volume over the last 12 months increased by 26% to $203 billion, providing merchants and consumers worldwide a faster, safer way to pay and be paid. PayPal is fully localized in 26 currencies, is available in 203 markets worldwide and has relationships with 15,000 financial institutions.

In other words, PayPal is a company with burgeoning potential thanks to its extensive global reach and its incredibly strong financial performance.

The payments industry is one that has delivered massive benefits to shareholders through the years -- since it went public in 2006, MasterCard (NYSE:MA) is up an astonishing 1,800% -- and the initial signs indicate PayPal should continue that trend in the years to come.

But investing in an IPO can always be tricky, and with so much focus on the payments industry in recent months, one has to wonder whether the demand for PayPal will drive up the price to unsustainable levels.

As a result, I'll be closely watching PayPal, because if the price is justifiable, then one has to think it will make for a sensible investment. 

In 2015, the launch of the Apple (NASDAQ:AAPL) Watch (rumored to come in the second quarter) will be a pivotal moment for the tech giant, as well as the fledgling wearables market.

The device will be the company's first new product line launch without Steve Jobs, and it represents a way for Apple to diversify beyond iPhones and iPads, which respectively accounted for 56% and 13% of its top line last quarter. Forecasts for the Apple Watch's first year sales vary widely, from 10 million units (Gene Munster, Piper Jaffray) to 60 million units (Katy Huberty, Morgan Stanley).

Based on the high end of that forecast, and a base price of $350 per unit, the Apple Watch could account for up to 3% of Apple's projected 2015 revenue of $210.7 billion. However, pricey wristbands will likely double or triple the price per unit, which means Apple Watch could account for nearly 10% of the company's annual revenue in a best-case scenario. If it sells well, Apple Watch could also tether more users to its Apple Pay, HealthKit, and HomeKit ecosystems.

The Apple Watch is also widely expected to turn smart watches from niche geek devices into mainstream ones. If Apple fails to do so, lofty projections -- such as ON World's forecast of smartwatch shipments soaring from 4 million in 2013 to 330 million in 2018 -- could be completely off the mark.

Todd Campbell
So far, the second open-enrollment period for the Obamacare health insurance exchanges has gone off without a hitch. The exchanges have signed up more than 6.4 million people in their first month, including 1.9 million new members, but what I'll be watching closely is how the next few months shake out.

That's because a surge in enrollment could mean big bucks for America's two largest health insurers in 2015. UnitedHealth Group (NYSE:UNH) and Anthem (NYSE:ANTM) are both participating broadly in the exchanges this year, and if the exchanges can exceed projections for 9 million members, both companies could see revenue jump.

Last year, UnitedHealth took a cautious approach to the exchanges, offering plans in just four states. This year, they offered plans in 24 states. Anthem has remained active, offering plans in 14 states in both years. The industry has indicated it expects to generate 3% to 5% margins off those plans over time. Since the average bronze level premium last year was $2,448, every million people who sign up through the exchanges should be worth at least $2.4 billion in industry-wide premium revenue, which, at a 3% margin would mean an additional $73 million in industry-wide profit per million members. That's enough of a needle-mover to get my attention.