Account aggregators are apps that let you see and track all your savings and expenditures together in one place. One example is Florida-based Wealth.com, which collects a whopping 7 years’ worth of transactions from your bank accounts, credit cards, and investments and serves it up in tantalizing pie charts.

“Wealth.com lets me analyze my spending patterns,” says customer Adrienne Hyslop. “It showed me how much I was spending on lattes and banking fees. It helped me stick to a budget, be thrifty, and save for my kids’ college education.”

But finance columnist Elsa Balka counsels caution. “Read your banking contract,” she says. “Using an aggregator involves disclosing your client number and password to a third party. That puts you in default of your online banking agreement. By voluntarily sharing this data with a party other than the bank, you void the bank’s guarantee that it will insure your investments against any possible fraudulent use.” Ms. Balka adds that account aggregators are typically US companies, storing your data across the border where it’s not subject to Canadian laws.

Consumer ombudsman Laurelei Reynolds has investigated the convenient “in-house” aggregators provided by the big banks themselves, such as Hexagon Bank’s quick-and-easy MoneyViewer app, integrated into the financial giant’s online banking platform. Customers who click the MoneyViewer link automatically launch an aggregator whose use is covered by a separate section of the online banking contract. There, Reynolds finds complex stipulations that compromise the consumer’s legal right to compensation if data or identity theft occurs. “Yes, MoneyViewer is bank-friendly, not ‘third-party,’” she concedes. “Still, bear in mind, if a consumer must breach her contract in order to use the product or service that the contract promises to provide, then the contract is unfair.”

That’s welcome news to Roald Weiss, CEO of Wealth.com. “Our security protocols are state-of-the-art,” Weiss says. “We use the same encryption techniques as the army. The real reason the big banks don’t want you using our product is that we reveal their hidden fees. We show you what they’re actually charging.”