Today was one of those days that was going to start out soft, but a key analyst upgrade saved the day. There was actually no early economic data, and traders are putting on their pre-earnings trades. Here is a quick look at the earnings previews for this week's key technology stocks and for this week's key financial stocks.

Here were today's unofficial closing bell levels:

Dow 8,313.92 +167.40 (2.05%)
S&P 500 901.05 +21.92 (2.49%)
Nasdaq 1,793.21 +37.18 (2.12%)

Top Analyst Calls

Over the past couple weeks, the shares of CardioNet (NASDAQ: BEAT) have plunged from $17 to $5.84. The problems started with a grim earnings report.

Unfortunately, today we got some more bad news: Highmark Medicare Services has lowered the reimbursement rate for CardioNet's services. On the news, the stock price is down by a third.

CardioNet develops sophisticated technologies to monitor heart rhythms using mobile devices. The upshot is that physicians can better diagnose and treat patients.

While CardioNet's devices are tremendously helpful, they come at a premium cost. However, in light of the recession and impending health care reforms, the outlook does look cloudy for the company. In fact, based on the recent change in reimbursements, CardioNet has withdrawn its 2009 earnings outlook.

Tom Taulli is the author of various books, including The Complete M&A Handbook and the founder of BizEquity, a free online business valuation tool for small businesses. You can reach him at his personal blog.

This post was written by Minyanville contributor Steve Smith.

Shares of CardioNet (NASDAQ: BEAT) shares are off $0.20 to $18.60 and option volume is three times the daily average. The focus is buying in the June $17.50 put which has seen over 5,100 contracts trade, 90% of which occurred at the ask, and exceeds prior open interest of if 1,018 contracts. This new put buying is driving up implied volatility 14% to the 65% level this morning.

CREE Inc. (NASDAQ: CREE) shares are up over 12% to $31.30 after the electronics parts manufacturer pre-announced and raised guidance. Options running 3X the daily average with 85% of trades on the call side. Active strikes are the include June $30 call and July $30 calls, with latter's volume exceeding strike's of 295 exceeding prior open interest. Notable is buying in longer dated series; the Sep $30 call, Dec $35 call and Jan 2010 $30 call have all traded over 200 contracts all of which exceed their strike's prior open interest.

Patriot Coal (NYSE: PCX) is up 19 cents to $9.15 and 2,500 Jun 10 calls traded. Nearly all the volume has been done at the asking price suggesting this speculative call buying.

MOST NOTEWORTHY: Cardionet, Molson Coors and TIM Participacoes were today's noteworthy initiations:

• Cardionet (NASDAQ: BEAT) initiated with an Overweight, target $29 at Thomas Weisel, who believes Cardionet is well positioned for future growth in the ambulatory monitoring market.
  
• Molson Coors Brewing Co. (NYSE: TAP) was initiated with a Market Perform, target $61 at BMO Capital.
  
• TIM Participacoes (NYSE: TSU) was re-initiated with an Outperform at Bear Stearns.

OTHER INITIATIONS:

• Invesco (NYSE: IVZ) was initiated with an Overweight at J.P. Morgan.
• Orion Marine Group (NASDAQ: OMGI) was initiated with a Buy, target of $18, at SMH Capital.
• Seattle Genetics Inc. (NASDAQ: SGEN) was initiated with a Neutral, target of $12, at Bank of America.

MOST NOTEWORTHY: Visa, Cardionet and Motorola were today's noteworthy initiations:

• RBC initiated Visa Inc (NYSE: V) with an Outperform based on margin expansion opportunities, the secular growth story towards electronic payments, lack of credit risk, and international opportunities. Piper started Visa with a Neutral rating. While the firm believes that Visa should generate long-term earnings growth and free cash flow, the firm thinks that Visa's valuation has increased the risk that strong earnings growth may not meet investors' expectations. However, the firm believes that Visa can still post strong results despite the U.S. consumer slowdown. Goldman initiated Visa with a Buy rating and $90 target and Morgan Stanley started shares with an Equal Weight rating and $75 target.
• Citigroup rated Cardionet Inc (NASDAQ: BEAT) a Buy, citing favorable arrhythmia monitoring trends. The firm has a $26 target on Cardionet.
• Motorola Inc (NYSE: MOT) was assumed with an Equal Weight rating and $75 target at Morgan Stanley on valuation.

OTHER INITIATIONS:

• Merriman initiated Netezza Corporation (NYSE: NZ) with a Neutral rating.
• Credit Suisse started Cascal N.V. (NYSE: HOO) with a Neutral rating and $11.65 target.

An arrhythmia is the result of an abnormal heart rhythm, which is caused by problems with electrical signals. In the U.S., roughly 4 million people who have the ailment. And it results in more than 780,000 hospitalizations as well as 480,000 deaths per year.

Fortunately, CardioNet has a solution. And, this week the company has filed to go public.

Basically, CardioNet has an ambulatory, real-time outpatient system that monitors clinical data. In fact, CardioNet has spent roughly $200 million in R&D to build the system. The capabilities include: a wireless data network, complex software, and a 24/7 service center. There is also a lightweight sensor for patients.

A recent clinical study shows that the CardioNet system detected clinically significant arrhythmias close to three times as often as traditional approaches.

CardioNet launched its system in early 2003. So far, there are more than 80,000 patients enrolled. What's more, last year the revenues were $54.7 million and there was a net loss of $5.9 million.

The lead underwriter on the IPO is Citigroup (NYSE: C) and the proposed ticker is "BEAT." The prospectus is located on the SEC website.

To check out more IPO filings, click here.

Tom Taulli is the author of various books, including the Complete M&A Handbook and the EDGAR-Online Guide to Decoding Financial Statements.