No question about it. We have become a mobile society. We are active, busy, and we want our information fast.  The average attention span of a reader is  less than 3 seconds.  That is all you have to catch their attention. Blogs, such as this are different because you came here searching for a specific topic and you want more information. But in marketing and advertising, people are in the scan mode. "Catch my attention and  I'm only giving you a second or two to do it in".  So how does a SMB accomplish this with little or no budget?
First you need to understand mobility marketing. In a nutshell we are talking about  reaching your customer through their smartphone.  We could the tablet as well  but for sake of discussion lets focus on the smartphone. Smartphones are the offce for today's executives and our population in general.  They get their news, email, videos, texts, web, and we have have apps (applications) to cover specific items of interest.  Most will work off wi-fi and wi-fi is pretty much available everywhere today. Wi-fi gives the user a smoother and faster experience in data load.  Ok great so now we know why we need to market to these mobile users, how do I do it without investing a huge amount of money?
Without spending a lot of time on each topic, I will list some general easy inexpensive methods and you can explore what will work best for you. Many of these topics you can find on the web if you want more information or if you have the budget your local marketing firm can help.  I will be happy to provide more inormation if you email me. 

Make sure your website is mobile compatible.  If your web site has not received  attention in the past few years, chances are it is not formatting to smart phones.  Make sure it does. check with your server host provider. Nothing worse than having your web site being checked on by a potential customer and they have to tap or scroll through  a maze to get their information. You will lose them in a hurry.
Use QR codes. These can be made free on the web.  What are they? Quick Response codes are scanned by smartphone users.  You can get  QRs to your clients or customers  by your email, web Advertisng, postcards, or  send it  via text. When they scan it via their smartphone camera,  the code takes them to whatever you want it to. Your web site, Youtube, your email address, whatever. Just make the link worthwhile. A special offer, discount, a promotional video. Pretty coool right?  I place them on my business cards.
Email. Emails are the least expensive way to reach your customers but market smart with them. use newsletter templates or send a offer. Make the email attractive to read. Remember  that 3 second rule?  Have a catchy headline, like "Free Offer" "Limited time" ect. Put that QR code there; Scan this for free mechandise or something similar.
SMS.  I have mixed feelings about texts in marketing.  Personally I find them annoying but others say they work. I consider sms texts from businesses like spam in email. Either you love it or hate it. Before you say, that is time consuming, There are software programs that will "auto" send SMS texts to reach a mass target.  Keep in mind you are burning up their data so make your texts catchy. (Most people today have an unlimited text plan)
Google Ad words-Mobile. Google Ad words are a good way to get your message out and just pay per click.  You can target specific markets or verticals.  Again, your ad  hits certain web sites you want to reach. Go to Google's  web site for more information.
Antalytics-SEO. Overhaul your web site and use Google antalytics to utilize "key words" and beef up your search engine optimization. This in turn will allow those with web on their smart phones to find you and your products or services easier giving you more "hits".
E-Commerce.  Market your business on the web.  If you have products or services to offer, put it on the web. and allow credit card transactions if possible.  Today's web sites are very secure to conduct business on line. Yes, there will always be some risk of hackers, but choose a good web hosting service. If you market on the web, that customer sitting at a airport between flights or sitting on the beach in Florida relaxing may be just thinking about something you have to offer.
  In conclusion, the above tips are the most popular but not all inclusive.  Develop a campagin, keep it all in theme, and design it so you can track your ROI.   Mobile marketing is not rocket science but you have to understand that the smartphone user is a "smart user" of his "smartphone".  Good luck!